LWC Interview Questions

Hello everyone, Welcome in Lightning Web Component Worlds...!! 

As Salesforce world is moving towards Lightning Web components (LWC), So today I will share the important and scenario-based LWC interview questions with detailed answers, examples, and explanations with you.

Asking simple straightforward questions in Salesforce is history. Few years back Salesforce certified people were very less. Hence criteria was just to check whether that person know about Salesforce or not.

So questions used to be:
•  What are Lightning Web Components (LWC)?
•  What is Lightning Framework in Salesforce?
•  How is LWC different from Aura?
•  What is the use of a Lightning Component Framework?
•  In how many ways can lightning components be made?
•  What are the different Lightning page types?
etc.

If you notice above questions are crisp to the point. But now since in market there are many Salesforce certified people above style of interview doesn't work. One could easily memories these.

Now the style of asking questions is different for the interviewer. There is more focus on asking real time scenario questions rather than how etc.

Check Scenario Based LWC Interview Questions as one can have the theoretical knowledge. But the recruiters also check for scenario-based knowledge or Practical knowledge. Recruiters always ask tricky questions on the problems that one can face during implementation.

Only the person which has faced the problems while execution can only answer the questions.

In this comprehensive article, we will explore some of the most important interview questions related to Lightning Web Components (LWC). We will provide detailed explanations and examples to help you grasp the concepts and prepare effectively for your LWC interviews.


Why LWC?

As the Salesforce platform continues to evolve, LWC has emerged as a game-changer in web development. LWC leverages modern web standards like HTML, CSS, and JavaScript to build lightning-fast, modular, and scalable web applications. With its focus on performance, reusability, and ease of development, LWC has become the go-to framework for many Salesforce developers.


 MIND IT !

The Importance of Interview Preparation

Preparing for an LWC interview can be an overwhelming task. It requires a solid understanding of LWC concepts, best practices, and hands-on experience. To help you in your journey, we have curated a comprehensive list of interview questions that cover a wide range of topics related to LWC.

In this blog series, I have tried to cover all important and scenario-based LWC Interview Questions which are often asked by LWC Developer in an interview.


 Interview Series

Let start the interview series on Lightning Web Components (Between Interviewer & Interviewee).

 Interviewer: What are Lightning Web Components (LWC)?


 Interviewee: LWC is a framework developed by Salesforce for building web applications on the Salesforce platform. It uses web standards like HTML, CSS, and JavaScript to create reusable and high-performing components.

Example Code : html

Explanation: In the example code above, we have a basic LWC component that displays a simple greeting message.


 Interviewer: How do LWC components differ from Aura components?


 Interviewee: LWC components are the next generation of components in the Salesforce ecosystem, replacing Aura components. LWC components offer better performance, enhanced reusability, and improved development productivity compared to Aura components.

Example Code : javascript

import { LightningElement } from 'lwc';

export default class HelloWorld extends LightningElement {
  greeting = 'Hello, Lightning Web Components!';
}

Explanation: In the example code above, we have a simple LWC component that defines a property called "greeting" and assigns it a value. This property can be accessed and displayed in the component's template.


 Interviewer: Explain the concept of data binding in LWC.


 Interviewee: Data binding in LWC establishes a connection between the component's JavaScript code and its HTML template. It enables dynamic updates and synchronization of data between the component's properties and the UI.

Example Code :

html

javascript

import { LightningElement } from 'lwc';

export default class HelloWorld extends LightningElement {
  greeting = 'Hello, Lightning Web Components!';
}

Explanation: In the example code above, we have a simple LWC component that binds the "greeting" property to the <h1> tag in the template. Any changes to the "greeting" property will automatically reflect in the UI.


 Interviewer: How do you communicate between LWC components?


 Interviewee: LWC provides various methods for component communication. These include property binding for parent-child communication, events for child-parent communication, and the publish-subscribe pattern for communication between unrelated components.

Example Code : html

javascript

// Parent Component JS
import { LightningElement } from 'lwc';

export default class ParentComponent extends LightningElement {
  parentMessage = 'Hello from Parent';

  handleChildEvent(event) {
    // Handle child event
    const message = event.detail;
    // Do something with the message
  }
}

html

javascript

// Child Component JS
import { LightningElement, wire } from 'lwc';

export default class ChildComponent extends LightningElement {
  handleClick() {
    const message = 'Hello from Child';
    this.dispatchEvent(new CustomEvent('customevent', { detail: message }));
  }
}

 Interviewer: How do you handle user input in LWC?


 Interviewee: LWC provides various mechanisms to handle user input, such as using event handlers, two-way data binding, and reactive properties. Event handlers can be used to capture user actions like button clicks or input changes.

Example Code : html

javascript

import { LightningElement, track } from 'lwc';

export default class UserInputExample extends LightningElement {
  @track username = '';

  handleInputChange(event) {
    this.username = event.target.value;
  }
}

Explanation: In the example code above, we have an input field where the user can enter their username. The 'handleInputChange' method is called on every input change, updating the 'username' property and displaying the entered value below the input field.


 Interviewer: How can you conditionally render a part of the template in LWC?


 Interviewee: Conditional rendering in LWC can be achieved by using the `if:true` or `if:false` directives in the template. You can conditionally show or hide an element based on a boolean expression.

Here's how it works:

Use the `if:true` directive to render an element if the provided expression evaluates to `true`. If the expression is `false`, the element will not be rendered.

Example Code : html

javascript

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
  isRendered = true;
}

In this example, the `<p>` element will be rendered because the `isRendered` property is set to `true`.

Use the `if:false` directive to render an element if the provided expression evaluates to `false`. If the expression is `true`, the element will not be rendered.

Example Code : html

javascript

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
  isHidden = true;
}

In this example, the `<p>` element will be rendered because the `isHidden` property is set to `true`, and the `if:false` directive renders the element when the expression is `false`.

By using these conditional rendering directives, you can control the visibility of elements in your LWC component based on specific conditions. This provides flexibility in dynamically showing or hiding parts of the template based on the state of your component or other variables.


 Interviewer: How can you iterate over a list and render elements dynamically in LWC?


 Interviewee: In LWC, you can use the `for:each` directive along with the `iterator` property to iterate over a list and dynamically render elements based on the list items.

Example Code : html

javascript

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
  itemList = [
    { id: 1, name: 'Item 1' },
    { id: 2, name: 'Item 2' },
    { id: 3, name: 'Item 3' },
  ];
}

In this example, the `<template>` element with the `for:each` directive iterates over the `itemList` array. For each item in the array, it generates a `<p>` element with the `key` attribute set to the item's `id` and displays the item's `name` as the content of the `<p>` element.

Use the `for:item` directive to specify a variable that represents each item in the iteration.

In the example above, `for:item="item"` assigns the current item in the iteration to the `item` variable. You can then use this variable within the template to access the properties of each item.

By using the `for:each` directive, you can dynamically generate elements in the template based on the items in the list. This allows you to render a variable number of components or HTML elements based on the data you have, providing flexibility in building dynamic and data-driven UIs in your LWC component.


 Interviewer: How can you communicate between parent and child components in LWC?


 Interviewee: Communication between parent and child components in LWC can be achieved through property binding and event handling. The parent component can pass data to the child component using property binding, and the child component can notify the parent component of any events using custom events.

Parent Component:

Example Code : html

javascript

import { LightningElement } from 'lwc';

export default class ParentComponent extends LightningElement {
  parentMessage = 'Hello from parent';

  handleEvent(event) {
    const eventData = event.detail;
    // Handle event data from child component
  }
}

Child Component:

javascript

import { LightningElement } from 'lwc';

export default class ChildComponent extends LightningElement {
  message = 'Hello from child';

  handleClick() {
    const customEvent = new CustomEvent('customevent', { detail: 'Event data' });
    this.dispatchEvent(customEvent);
  }
}

Explanation: In the example code above, we have an input field where the user can enter their username. The 'handleInputChange' method is called on every input change, updating the 'username' property and displaying the entered value below the input field.


 Interviewer: What is the role of the wire service in LWC?


 Interviewee: The wire service in LWC enables efficient data retrieval and synchronization with Salesforce data sources. It handles caching, background execution, and automatic UI updates, resulting in better performance and responsiveness.

Example Code : javascript

import { LightningElement, wire } from 'lwc';
import { getRecord } from 'lightning/uiRecordApi';

const FIELDS = ['Account.Name', 'Account.Phone', 'Account.Website'];

export default class AccountDetails extends LightningElement {
  @wire(getRecord, { recordId: '001xxxxxxxxxxxxxxx', fields: FIELDS })
  account;

  get accountName() {
    return this.account.data ? this.account.data.fields.Name.value : '';
  }
}

Explanation: In the example code above, we have a component that uses the wire service to fetch and display account details from Salesforce. The 'getRecord' wire adapter retrieves the specified fields from the record with the given ID.


 Interviewer: How do you handle errors and exceptions in LWC?


 Interviewee: Error handling in LWC can be done using try-catch blocks or by leveraging the onError lifecycle hook. You can catch exceptions and display appropriate error messages to the user, ensuring a smooth user experience.

Example Code : html

Explanation: In the example code above, we have a try-catch block that wraps the code that might throw an exception. If an exception occurs, it is caught in the catch block, allowing you to handle the error gracefully.


 Interviewer: What are the lifecycle hooks in LWC, and how do they work?


 Interviewee: LWC provides various lifecycle hooks that allow you to perform actions at specific stages of a component's lifecycle. Examples include connectedCallback, renderedCallback, and disconnectedCallback. These hooks help manage component initialization, rendering, and cleanup.

Example Code : javascript

import { LightningElement } from 'lwc';

export default class LifecycleExample extends LightningElement {
  connectedCallback() {
    // Perform initialization tasks when the component is connected to the DOM
  }

  renderedCallback() {
    // Perform tasks after the component has been rendered or updated
  }

  disconnectedCallback() {
    // Perform cleanup tasks when the component is removed from the DOM
  }
}

Explanation: In the example code above, we have a component that demonstrates the usage of connectedCallback, renderedCallback, and disconnectedCallback. These hooks allow you to execute custom logic at specific stages of the component's lifecycle.


 Interviewer: How do you use LWC lifecycle hooks to fetch data from an external source?


 Interviewee: To fetch data from an external source using LWC lifecycle hooks, you can use the `connectedCallback()` method. The `connectedCallback()` lifecycle hook is called when the component is inserted into the DOM tree. This is a suitable place to perform data fetching operations, as it ensures the component is ready to interact with the DOM.

Here's an example of how you can use the `connectedCallback()` method to fetch data from an external source:

Example Code : javascript

// dataFetchExample.js
import { LightningElement, track } from 'lwc';
import fetchDataFromExternalSource from '@salesforce/apex/ExampleController.fetchDataFromExternalSource';

export default class DataFetchExample extends LightningElement {
  @track data; // Use @track to track changes to the data variable

  connectedCallback() {
    this.loadDataFromExternalSource();
  }

  loadDataFromExternalSource() {
    fetchDataFromExternalSource()
      .then(result => {
        // Process the data as needed
        this.data = result;
      })
      .catch(error => {
        // Handle error, if any
        console.error('Error fetching data: ', error);
      });
  }
}

In this example, the `connectedCallback()` method is overridden in the LWC component. Inside this method, the `loadDataFromExternalSource()` function is called to perform the data fetching operation. The `fetchDataFromExternalSource()` method is an Apex method annotated with `@AuraEnabled` that retrieves data from an external source, such as an Apex class, a REST endpoint, or a third-party API.

By using the `connectedCallback()` hook, the data will be fetched as soon as the component is inserted into the DOM tree, ensuring that the component is ready to display the data when it becomes available.


 Interviewer: How can you optimize the performance of LWC applications?


 Interviewee: To optimize LWC application performance, consider techniques such as minimizing DOM manipulations, using reactive properties efficiently, implementing pagination and lazy loading for large data sets, and applying caching strategies for frequently accessed data.

Example Code : javascript

// Reduce unnecessary re-renders using reactive properties and getters
import { LightningElement, track } from 'lwc';

export default class PerformanceOptimizationExample extends LightningElement {
  @track data = [];

  get processedData() {
    // Perform complex calculations or data transformations
    return this.data.map((item) => item * 2);
  }
}

Explanation: In the example code above, the 'processedData' getter performs complex calculations or data transformations on the 'data' property. By utilizing getters, you can avoid redundant computations and improve performance.


 Interviewer: How can you reuse LWC components in multiple projects?


 Interviewee: LWC promotes code reusability through the creation of reusable components. You can package these components as Salesforce packages or use them in different projects within your organization, reducing development time and effort.

Example Code : javascript

// LWC Component 1
import { LightningElement } from 'lwc';

export default class Component1 extends LightningElement {
  // Component 1 logic
}

javascript

// LWC Component 2
import { LightningElement } from 'lwc';

export default class Component2 extends LightningElement {
  // Component 2 logic
}

Explanation: In the example code above, we have two LWC components, 'Component1' and 'Component2', each with its own logic. These components can be reused in multiple projects by importing them and leveraging their functionality.


 Interviewer: How do you write unit tests for LWC components?


 Interviewee: LWC provides a testing framework that allows you to write unit tests for your components. You can use tools like Jest and Lightning Testing Service (LTS) to perform unit testing and ensure the quality and reliability of your code.

Example Code : javascript

// LWC Component
import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
  // Component logic
}

javascript

// Jest Unit Test
import { createElement } from 'lwc';
import MyComponent from 'c/myComponent';

describe('c-my-component', () => {
  it('renders correctly', () => {
    const element = createElement('c-my-component', { is: MyComponent });
    document.body.appendChild(element);

    expect(element.shadowRoot.textContent).toBe('Hello, LWC!');
  });
});

Explanation: In the example code above, we have an LWC component 'MyComponent' and a Jest unit test that verifies the correct rendering of the component. By creating an instance of the component and asserting the expected output, you can ensure its functionality.


 Interviewer: What is the role of the Lightning Data Service in LWC?


 Interviewee: The Lightning Data Service (LDS) is a powerful feature in LWC that simplifies data management and reduces the amount of code needed for CRUD operations. It provides a standard way to access and manipulate Salesforce data without writing Apex code.

 MIND IT !

Lightning Data Service(LDS): Lightning Data Service is helpful to connect our component with data without actually calling, apex. We can use LDS to create, update, and delete our records when we have simple requirements which don’t require any complex logic to perform.


Example Code : html

Explanation: In the example code above, we have a form that utilizes the Lightning Data Service to create or update Account records. The 'lightning-record-edit-form' component handles the data operations, allowing users to input and save record details.


 Interviewer: How can you handle pagination in LWC?


 Interviewee: Pagination in LWC can be implemented using a combination of Apex methods, LDS, and UI controls. You can retrieve data in batches using Apex queries, display a subset of records, and provide navigation controls to switch between pages.

Example Code : html

javascript

import { LightningElement, wire } from 'lwc';
import getAccounts from '@salesforce/apex/AccountController.getAccounts';

const PAGE_SIZE = 10;

export default class PaginationExample extends LightningElement {
  currentPage = 1;
  visibleData = [];
  columns = [
    // Define columns
  ];

  @wire(getAccounts, { pageSize: PAGE_SIZE })
  wiredAccounts({ data, error }) {
    if (data) {
      // Handle retrieved data
      this.visibleData = data;
    } else if (error) {
      // Handle error
    }
  }

  handlePrevious() {
    // Handle previous page logic
  }

  handleNext() {
    // Handle next page logic
  }
}

Explanation: In the example code above, we have a pagination example where the 'lightning-datatable' component displays a subset of account records. The user can navigate between pages using the "Previous" and "Next" buttons, triggering the corresponding methods.


 Interviewer: How do you handle record deletion in LWC?


 Interviewee: Record deletion in LWC can be done using the Lightning Data Service or by making server-side calls using Apex. You can use the 'lightning-record-edit-form' component or implement custom logic to delete records based on user interactions.

Example Code : html

javascript

import { LightningElement } from 'lwc';

export default class DeleteRecordExample extends LightningElement {
  recordId = '001xxxxxxxxxxxxxxx';

  handleSuccess(event) {
    // Handle successful record deletion
  }
}

Explanation: In the example code above, we have a form that uses the 'lightning-record-edit-form' component to delete an Account record. When the form is submitted, the 'handleSuccess' method is triggered, allowing you to handle the successful deletion of the record.


 Interviewer: How can you handle component-level events in LWC?


 Interviewee: Component-level events in LWC enable communication between sibling components or unrelated components. You can define custom events in a component and use event listeners or event propagation to handle and respond to those events.

Example Code : html

javascript

// Parent Component JS
import { LightningElement } from 'lwc';

export default class ParentComponent extends LightningElement {
  handleEvent(event) {
    // Handle the custom event
  }
}

html

javascript

// Child Component JS
import { LightningElement } from 'lwc';

export default class ChildComponent extends LightningElement {
  fireEvent() {
    const customEvent = new CustomEvent('customevent', {
      detail: 'Event data',
    });
    this.dispatchEvent(customEvent);
  }
}

Explanation: In the example code above, we have a parent component that listens for a custom event, 'customevent', fired by a child component. When the event is fired, the 'handleEvent' method in the parent component is triggered, allowing you to handle the event data.


 Interviewer: How can you handle CSS styling in LWC?


 Interviewee: CSS styling in LWC can be done using inline styles, static resources, or CSS files. You can apply styles directly to elements using the 'style' attribute, import and apply stylesheets, or use CSS classes defined in your component's styles.

Example Code : html

css

/* CSS File or Component Style */
.custom-style {
  color: blue;
  font-size: 18px;
}

Explanation: In the example code above, we have an example of inline styling and class styling. The '<h1> 'element uses an inline style with the 'color' property set to red. The '<div>' element applies a class style with the 'color' property set to blue and the 'font-size' property set to 18 pixels.


 Interviewer: How do you handle CSS scoping in LWC?


 Interviewee: In Lightning Web Components (LWC), CSS scoping is automatically handled by the framework to ensure that styles defined in one component do not interfere with styles in other components. This feature is called "CSS scoping" or "CSS encapsulation". It helps to create more modular and maintainable components by preventing unintended style overrides and conflicts.

Here's how CSS scoping works in LWC:

Scoped CSS: By default, the CSS styles defined within an LWC component's style block only apply to the elements within that component's template. The styles are scoped to the component, meaning they won't affect other components on the same page.

Shadow DOM: LWC uses the Shadow DOM to encapsulate component styles. The Shadow DOM creates a separate DOM subtree for each component, isolating its styles, DOM structure, and behavior from the rest of the page.

Selectors: Selectors defined in the component's style block target only the elements within the component's template. For example, if you define a class selector in the style block, it will apply only to the elements with that class inside the component.

No Global Styling: Styles defined in one LWC component won't inadvertently affect other components or the global CSS of the parent application.

Here's an example of CSS scoping in LWC:

In this example, the styles defined in the `<style>` block are scoped to the `scopedComponent` and will only apply to the elements within that component's template. If you use this component multiple times on the same page or in different pages, the styles won't conflict with each other.

LWC's built-in CSS scoping ensures that styles are isolated within the component, making it easier to manage and reason about the styling of individual components in a complex application. This approach follows modern web development best practices and helps create more maintainable and reusable components.


 Interviewer: How can you handle conditional rendering in LWC?


 Interviewee: Conditional rendering in LWC can be done using if-else statements, ternary operators, or by evaluating expressions in the template. You can conditionally show or hide elements, render different components, or apply different styles based on the specified conditions.

Example Code : html

javascript

import { LightningElement, track } from 'lwc';

export default class ConditionalRenderingExample extends LightningElement {
  @track showElement = true;
}

Explanation: In the example code above, we have a template with a conditional rendering using the 'if:true' directive. The '<p>' element is only rendered if the 'showElement' property is set to true.


 Interviewer: How do you handle form validation in LWC?


 Interviewee: Form validation in LWC can be achieved using HTML5 validation attributes, JavaScript validation, or by leveraging the 'lightning-input' component's built-in validation. You can validate input fields, display error messages, and prevent form submission until valid data is provided.

Example Code : html

javascript

import { LightningElement, track } from 'lwc';

export default class FormValidationExample extends LightningElement {
  @track showError = false;

  handleInputChange(event) {
    // Validate input and set showError accordingly
  }

  handleSubmit() {
    if (this.showError) {
      // Prevent form submission
      return;
    }
    // Submit form data
  }
}

Explanation: In the example code above, we have a form that validates an email input field. The field uses HTML5 validation attributes such as 'required' and 'pattern' to enforce input rules. The handleInputChange method 'handles input changes' and sets the 'showError' property based on the validity of the input.


 Interviewer: How can you communicate with the server in LWC?


 Interviewee: LWC provides various ways to communicate with the server, such as making Apex method calls, using the wire service, or making HTTP requests using the fetch API. You can retrieve data, perform CRUD operations, or integrate with external systems using these communication methods.

Example Code : javascript

import { LightningElement, wire } from 'lwc';
import getAccounts from '@salesforce/apex/AccountController.getAccounts';

export default class ServerCommunicationExample extends LightningElement {
  @wire(getAccounts)
  accounts;

  handleButtonClick() {
    // Make an HTTP request using the fetch API
    fetch('https://api.example.com/data')
      .then((response) => response.json())
      .then((data) => {
        // Handle the response data
      })
      .catch((error) => {
        // Handle any errors
      });
  }
}

Explanation: In the example code above, we have an example of server communication using the wire service and the 'fetch' API. The 'getAccounts' wire adapter retrieves account data from Apex, while the 'handleButtonClick' method makes an HTTP request to an external API, handling the response and errors accordingly.


 Interviewer: How do you handle event propagation in LWC?


 Interviewee: Event propagation in LWC can be controlled using the 'stopPropagation' method or by using the 'composed' property of custom events. By stopping event propagation, you can prevent parent or ancestor components from receiving the event.

Example Code : html

javascript

// Parent Component JS
import { LightningElement } from 'lwc';

export default class ParentComponent extends LightningElement {
  handleEvent(event) {
    // Handle the custom event
  }
}

html

javascript

// Child Component JS
import { LightningElement } from 'lwc';

export default class ChildComponent extends LightningElement {
  handleClick(event) {
    event.stopPropagation();
    // Fire the custom event
  }
}

Explanation: In the example code above, we have a parent component that listens for a custom event fired by a child component. By calling 'event.stopPropagation()' in the child component's event handler, the event propagation is stopped, preventing the parent component from receiving the event.


 Interviewer: How can you handle the aura integration in LWC?


 Interviewee: LWC supports seamless integration with Aura components using the Lightning Message Service (LMS). LMS enables communication between LWC and Aura components, allowing you to publish and subscribe to events across the component hierarchy.

Example Code : javascript

// LWC Component
import { LightningElement } from 'lwc';
import { ShowToastEvent } from 'lightning/platformShowToastEvent';

export default class LWCComponent extends LightningElement {
  handleButtonClick() {
    // Publish a toast message event
    const event = new ShowToastEvent({
      title: 'Success',
      message: 'LWC to Aura communication',
      variant: 'success',
    });
    this.dispatchEvent(event);
  }
}

xml

javascript

// Aura Component Controller
({
  handleButtonClick: function (component, event, helper) {
    // Handle the button click event
  },
  handleMessageReceived: function (component, event, helper) {
    // Handle the toast message event
  },
});

Explanation: In the example code above, we have an LWC component that publishes a toast message event using the 'ShowToastEvent'. The Aura component subscribes to the event using the Lightning Message Service (lightning:empApi) and handles the event in its controller.


 Interviewer: What is Lightning Message Service (LMS) in Salesforce?


 Interviewee: Lightning Message Service (LMS) in Salesforce is a powerful communication mechanism that enables different components, whether they are on the same page or on different pages, to exchange messages and data seamlessly.

LMS provides a way for Lightning Web Components (LWC), Aura components, and Visualforce pages to communicate with each other, facilitating cross-component communication without requiring a parent-child relationship between the components.

Key Features of LMS:

  1. Cross-Domain Communication: LMS allows components on different pages or within different frameworks (LWC, Aura, and Visualforce) to communicate. For instance, a component on one page can send a message, and another component on a different page can receive it.
  2. Decoupling of Components: It decouples the components, meaning components don't need to be aware of each other's presence. They just need to subscribe to the message channel and respond when necessary.
  3. Message Channels: Communication is facilitated via message channels, which are custom objects that define the structure of the message being passed. Components can publish or subscribe to messages on these channels.
  4. Framework Compatibility: LMS works across LWC, Aura components, and Visualforce, making it versatile and usable across the Salesforce platform.

How It Works:

  • Publish: A component can publish a message to a message channel.
  • Subscribe: Other components can subscribe to the same message channel to receive the message.
  • Message Channel: This acts as a medium for communication between different components.


 Interviewer: How can you handle the platform events in LWC?


 Interviewee: LWC provides built-in support for handling platform events using the Lightning Message Service (LMS). You can subscribe to platform events, receive event notifications, and perform actions based on the received events.

Example Code : javascript

// LWC Component
import { LightningElement } from 'lwc';
import { subscribe, unsubscribe, onError } from 'lightning/empApi';

export default class LWCComponent extends LightningElement {
  channelName = '/event/My_Event__e';

  connectedCallback() {
    // Subscribe to the platform event
    const messageCallback = (response) => {
      // Handle the received event
    };
    subscribe(this.channelName, -1, messageCallback).then((response) => {
      // Handle the subscription response
    });
  }

  disconnectedCallback() {
    // Unsubscribe from the platform event
    unsubscribe(this.subscription).then((response) => {
      // Handle the unsubscription response
    });
  }
}

Explanation: In the example code above, we have an LWC component that subscribes to a platform event ('My_Event__e'). The 'subscribe' function is used to establish the subscription and provide a callback function to handle the received event. The 'unsubscribe' function is called in the 'disconnectedCallback' to unsubscribe from the event when the component is no longer in use.


 Interviewer: How can you handle record updates in LWC?


 Interviewee:  LWC provides several approaches to handle record updates, such as using the Lightning Data Service (LDS), invoking Apex methods, or making HTTP requests. You can listen for changes in data, perform validations, and update the records accordingly.

Example Code : html

javascript

import { LightningElement, track } from 'lwc';

export default class RecordUpdateExample extends LightningElement {
  @track accountId;

  handleSuccess(event) {
    // Handle successful record update
    this.accountId = event.detail.id;
  }

  handleSubmit(event) {
    // Perform any pre-submission validation
  }

  handleError(event) {
    // Handle error during record update
  }
}

Explanation: In the example code above, we have a form that uses the 'lightning-record-edit-form' component to update an Account record. The form handles successful updates, pre-submission validations, and errors using the corresponding event handlers.


 Interviewer: How do you handle dependent picklists in LWC?


 Interviewee: Dependent picklists in LWC can be handled using the 'lightning-combobox' component and dynamically populating the picklist options based on the selected values. You can define data structures to store the available options, update the options based on the selected values, and manage the dependent relationships.

Example Code : html

javascript

import { LightningElement, track } from 'lwc';

export default class DependentPicklistExample extends LightningElement {
  @track selectedCountry;
  @track selectedState;
  countryOptions = [
    // Define country options
  ];
  stateOptions = [];

  handleCountryChange(event) {
    this.selectedCountry = event.detail.value;
    // Update state options based on selected country
    this.stateOptions = this.getStateOptions(this.selectedCountry);
  }

  handleStateChange(event) {
    this.selectedState = event.detail.value;
  }

  getStateOptions(country) {
    // Retrieve state options based on country
    return [];
  }
}

Explanation: In the example code above, we have an example of handling dependent picklists using the 'lightning-combobox' component. The 'handleCountryChange' method is triggered when the country selection changes, updating the state options based on the selected country. The 'handleStateChange' method captures the selected state value. The 'getStateOptions' method retrieves the state options based on the selected country.


 Interviewer: How can you handle file uploads in LWC?


 Interviewee:  File uploads in LWC can be achieved using the 'lightning-file-upload' component and Apex methods. You can allow users to select and upload files, handle the uploaded files on the server-side, and provide feedback to the user.

Example Code : html

javascript

import { LightningElement } from 'lwc';

export default class FileUploadExample extends LightningElement {
  recordId = '001xxxxxxxxxxxxxxx';

  handleUploadFinished(event) {
    const uploadedFiles = event.detail.files;
    // Handle uploaded files
  }
}

Explanation: In the example code above, we have a file upload example using the 'lightning-file-upload' component. When the user finishes selecting files, the 'handleUploadFinished' method is triggered, providing access to the uploaded files. You can then handle the files as needed, such as attaching them to a record or performing other operations.


 Interviewer: What are decorators in LWC?


 Interviewee:  Decorators in LWC are special JavaScript syntax that allows you to enhance the functionality of components or methods. They are prefixed with the @ symbol and can be used to perform tasks such as adding metadata, enabling wire service, applying access control, and more.

Example Code:javasript

import { LightningElement, api, wire } from 'lwc';
import { track } from 'lwc';

export default class MyComponent extends LightningElement {
  @api message;
  @track count = 0;

  @wire(getData)
  wiredData;
}

Explanation: In the example code above, the '@api' decorator is used to make the 'message' property accessible to parent components. The '@track' decorator ensures that changes to the 'count' property trigger re-rendering. The '@wire' decorator connects the 'wiredData' property to the result of the 'getData' wire adapter.


 MIND IT !

Here are some common decorators used in LWC:

@api: The '@api' decorator is used to expose a property or method of a Lightning web component to be publicly accessible to other components. It allows for component composition and facilitates communication between components.

Example Code:javasript

import { LightningElement, api } from 'lwc';

export default class MyComponent extends LightningElement {
  @api myProperty;
  @api
  myMethod() {
    // Method logic here
  }
}

@track:The '@track' decorator is used to track changes to a property in a reactive manner. When a tracked property is modified, the component's template is updated to reflect the changes automatically.

Example Code:javasript

import { LightningElement, track } from 'lwc';

export default class MyComponent extends LightningElement {
  @track myProperty = 'Initial value';

  handleClick() {
    this.myProperty = 'Updated value';
  }
}

@wire: The '@wire' decorator is used for declarative data binding and integration with Salesforce data. It allows you to retrieve data from an Apex method, a wire adapter, or a standard Lightning web component, and automatically updates the property in the component with the retrieved data.

Example Code:javasript

import { LightningElement, wire } from 'lwc';
import getAccountList from '@salesforce/apex/AccountController.getAccountList';

export default class MyComponent extends LightningElement {
  @wire(getAccountList)
  accounts;
}

@api get: The '@api get' decorator is used to create a getter for a property in a Lightning web component. It allows you to define custom logic for retrieving the value of a property when it is accessed.

Example Code:javasript

import { LightningElement, api } from 'lwc';

export default class MyComponent extends LightningElement {
  _myProperty;

  @api get myProperty() {
    return this._myProperty;
  }

  set myProperty(value) {
    this._myProperty = value;
    // Custom logic here
  }
}

@api set: The '@api set' decorator is used to create a setter for a property in a Lightning web component. It allows you to define custom logic for setting the value of a property when it is assigned a new value.

Example Code:javasript

import { LightningElement, api } from 'lwc';

export default class MyComponent extends LightningElement {
  _myProperty;

  @api get myProperty() {
    return this._myProperty;
  }

  @api set myProperty(value) {
    this._myProperty = value;
    // Custom logic here
  }
}

Decorators in LWC provide a powerful way to enhance and customize the behavior of Lightning web components. They enable reusability, encapsulation, and facilitate communication between components. By applying decorators, you can extend the functionality of components and create more flexible and modular code.


 Interviewer: What is the purpose of the '@api' decorator in LWC?


 Interviewee: The '@api' decorator in LWC is used to expose properties and methods of a component to other components in the hierarchy. It allows parent components to access and set values on the decorated properties and invoke decorated methods.

Example Code : javascript

import { LightningElement, api } from 'lwc';

export default class ChildComponent extends LightningElement {
  @api message;

  handleClick() {
    console.log('Message:', this.message);
  }
}

Explanation: In the example code above, the '@api' decorator is used to expose the message property to parent components. The parent component can set the value of message, and the child component can access it and perform actions, such as logging it to the console.


 Interviewer: How do you implement client-side caching in LWC?


 Interviewee: In Lightning Web Components (LWC), client-side caching can be implemented using the `@wire` decorator with the `refresh` parameter. The `refresh` parameter allows you to control when the cached data should be refreshed from the server. By setting `refresh` to `true`, you can force a refresh of the data on each component instantiation or when a specific variable changes.

Here's an example of how to implement client-side caching in LWC:

First, create the Apex class with the method you want to call:

// Apex class: AccountController.cls
public with sharing class AccountController {
    @AuraEnabled(cacheable=true)
    public static List<account> getAccounts() {
        // Simulate some time-consuming operation
        System.debug('Method called on the server.');
        try {
            Thread.sleep(3000);
        } catch (Exception ex) {
        }
        return [SELECT Id, Name, Industry FROM Account];
    }
}

Then, create the LWC component to call the Apex method with client-side caching:





// clientSideCaching.js
import { LightningElement, wire } from 'lwc';
import getAccounts from '@salesforce/apex/AccountController.getAccounts';

export default class ClientSideCaching extends LightningElement {
    @wire(getAccounts, { refresh: true }) // Set refresh to true to enable caching
    accounts;

    handleFetchAccounts() {
        // This method will call the Apex method again, but the cached data will be returned due to client-side caching.
        this.accounts = getAccounts({ refresh: true });
    }
}

In this example, we use the `@wire` decorator with the `refresh `parameter set to `true`. When the component is first loaded, the Apex method `getAccounts` is called, and the result is cached on the client-side. Subsequent calls to `getAccounts` from within the component (e.g., by clicking the "Fetch Accounts" button) will use the cached data unless `refresh` is explicitly set to `true`. This reduces the need for unnecessary server calls and improves the performance of the component.

 MIND IT !

Note that client-side caching is especially useful when dealing with data that doesn't change frequently or when you want to minimize the number of server calls in your LWC components. However, it's essential to consider the caching strategy based on your specific use case and data requirements.


 Interviewer: What is the difference between the '@api' and '@track' decorators in LWC?


 Interviewee: The '@api' and '@track' decorators serve different purposes in LWC. The '@api' decorator exposes properties and methods to other components, while the '@track' decorator enables reactivity and ensures updates to the property trigger re-rendering.

Example Code : javascript

import { LightningElement, api, track } from 'lwc';

export default class MyComponent extends LightningElement {
  @api message;
  @track count = 0;
}

Explanation: In the example code above, the '@api' decorator is used to expose the 'message' property to parent components. The '@track' decorator ensures that changes to the 'count' property trigger re-rendering.


 Interviewer: How does the '@wire' decorator work in LWC?


 Interviewee: The '@wire' decorator in LWC enables reactive data fetching and synchronization with the Salesforce backend. It connects the component's properties to wire adapters, which are functions that retrieve data from Apex controllers, Lightning Web Components, or external services.

Example Code : javascript

import { LightningElement, wire } from 'lwc';
import { getAccounts } from 'my/apexClass';

export default class MyComponent extends LightningElement {
  @wire(getAccounts)
  accounts;
}

Explanation: In the example code above, the '@wire' decorator is used to connect the accounts property to the getAccounts wire adapter, which retrieves data from an Apex class. The component automatically receives and updates the accounts property with the latest data from the wire adapter.


 Interviewer: How can you define a property with default values using decorators in LWC?


 Interviewee: You can define a property with default values using the '@api' and '@track' decorators in LWC. The '@api' decorator exposes the property to parent components, while the '@track' decorator ensures reactivity and updates to the property.

Example Code : javascript

import { LightningElement, api, track } from 'lwc';

export default class MyComponent extends LightningElement {
  @api message = 'Hello';
  @track count = 0;
}

Explanation: In the example code above, the `message` property is decorated with `@api` to expose it to parent components. It has a default value of `'Hello'`. The `count` property is decorated with `@track` to enable reactivity and has a default value of 0.


 Interviewer: How can you enforce access control on a method using decorators in LWC?


 Interviewee: You can enforce access control on a method using the `@api` decorator in LWC. By default, methods in LWC are private, but by decorating a method with `@api`, you make it accessible to other components.

Example Code : javascript

import { LightningElement, api } from 'lwc';

export default class MyComponent extends LightningElement {
  @api
  showPopup() {
    // Method implementation
  }
}

Explanation: In the example code above, the `showPopup` method is decorated with `@api` to make it accessible to other components. Parent components can invoke this method to show a popup or perform any desired action.


 Interviewer: How can you enable caching for a wire adapter using the `@wire` decorator in LWC?


 Interviewee: You can enable caching for a wire adapter using the `@wire` decorator by specifying the `cacheable` property and setting it to `true`. This allows the component to cache the data and use it for subsequent renders without making additional server calls.

Example Code : javascript

import { LightningElement, wire } from 'lwc';
import { getAccounts } from 'my/apexClass';

export default class MyComponent extends LightningElement {
  @wire(getAccounts, { cacheable: true })
  accounts;
}

Explanation: In the example code above, the `@wire` decorator is used to connect the `accounts` property to the `getAccounts` wire adapter with caching enabled. The component will fetch the data from the server initially, and subsequent renders will use the cached data without making additional server calls.


 Interviewer: How can you perform imperative data retrieval using the `@wire` decorator in LWC?


 Interviewee: The `@wire` decorator can also be used for imperative data retrieval by specifying a property to hold the result and a function to invoke the wire adapter imperatively.

Example Code : javascript

import { LightningElement, wire } from 'lwc';
import { getAccounts } from 'my/apexClass';

export default class MyComponent extends LightningElement {
  accounts;

  connectedCallback() {
    getAccounts()
      .then(result => {
        this.accounts = result;
      })
      .catch(error => {
        // Handle error
      });
  }
}

Explanation: In the example code above, the `connectedCallback` lifecycle hook is used to invoke the `getAccounts` wire adapter imperatively. The result is assigned to the `accounts` property, which can then be used in the component's template or logic.


 Interviewer: How can you make an asynchronous callout in LWC?


 Interviewee: In LWC, you can make asynchronous callouts to external services using the `fetch` function or by invoking Apex methods using the `@wire` decorator.

Example using `fetch`:

Example Code : javascript

import { LightningElement } from 'lwc';

export default class MyComponent extends LightningElement {
  makeCallout() {
    fetch('https://api.example.com/data')
      .then(response => response.json())
      .then(data => {
        // Handle response data
      })
      .catch(error => {
        // Handle error
      });
  }
}

Example using `@wire`:

Example Code : javascript

import { LightningElement, wire } from 'lwc';
import fetchData from '@salesforce/apex/Controller.fetchData';

export default class MyComponent extends LightningElement {
  @wire(fetchData)
  wiredData({ error, data }) {
    if (data) {
      // Handle response data
    } else if (error) {
      // Handle error
    }
  }
}

Explanation: In the example code above, we have a simple LWC component that defines a property called "greeting" and assigns it a value. This property can be accessed and displayed in the component's template.


 Interviewer: Explain the use of track and immutable in LWC.


 Interviewee: In Lightning Web Components (LWC), both track and immutable are used to manage the reactivity of properties in the component.

`@track` Decorator:

The `@track` decorator is used to make a property reactive in LWC. When a property is marked with `@track`, any change to its value triggers a re-render of the component, updating the corresponding parts of the template that use this property. It ensures that the component stays in sync with the data changes, and any updates are reflected in the UI.

Example:





// trackExample.js
import { LightningElement, track } from 'lwc';

export default class TrackExample extends LightningElement {
    @track count = 0;

    handleIncrement() {
        this.count++;
    }
}

In this example, the `count` property is marked with the `@track `decorator. When the "Increment" button is clicked, the `handleIncrement` method updates the count property. As a result, the template is automatically updated to reflect the new value of `count`.

`@immutable` Decorator:

The `@immutable` decorator is used to prevent direct modification of a property in LWC. When a property is marked with `@immutable`, you cannot directly modify its value after it has been initialized. This helps enforce better data encapsulation and prevents accidental changes to the property from outside the component.

Example:





// immutableExample.js
import { LightningElement, immutable } from 'lwc';

export default class ImmutableExample extends LightningElement {
    @immutable message = 'Initial message';

    handleUpdateMessage() {
        this.message = 'Updated message'; // This will throw an error due to the @immutable decorator.
    }
}

In this example, the `message` property is marked with the `@immutable` decorator. If you attempt to directly modify the `message` property in the `handleUpdateMessage` method, it will throw an error at runtime, preventing you from changing the value of the property.

 MIND IT !

Note that `@immutable` only prevents direct assignment to the property; you can still modify properties of an object marked as `@immutable`. If you need to enforce immutability for nested properties, you need to use other approaches like using `Object.freeze()`.

Both `@track`and `@immutable` decorators are essential tools for managing state and data reactivity in LWC components. Using them appropriately helps create more predictable and maintainable components in Salesforce Lightning.


 Interviewer: What are LWC getters and setters, and how are they used?


 Interviewee: In Lightning Web Components (LWC), getters and setters are special methods used to define and access component properties with custom behavior. They allow you to add additional logic when getting or setting the value of a property. Getters are used to retrieve the value of a property, and setters are used to update the value of a property. They provide a way to encapsulate the property's behavior and ensure that any required actions or validations are executed when the property is accessed or modified.

Here's an example of how to use getters and setters in LWC:





// getterSetterExample.js
import { LightningElement } from 'lwc';

export default class GetterSetterExample extends LightningElement {
    _count = 0; // Private variable to store the value

    // Getter for count property
    get count() {
        return this._count;
    }

    // Setter for count property
    set count(value) {
        // Perform any validations or actions before setting the value
        if (value >= 0) {
            this._count = value;
        }
    }

    handleIncrement(event) {
        // Get the value from the input and update the count property using the setter
        this.count = parseInt(event.target.value);
    }
}

In this example, we have a `count` property with a custom getter and setter. The getter (`get count()`) returns the private variable `_count`, and the setter (`set count(value)`) allows us to perform validations before updating the value of `_count`.

When the user enters a value in the `<lightning-input>` field, the `handleIncrement` method is called. It parses the input value as an integer and sets it to the `count` property using the custom setter. The setter ensures that the `count `property can only be updated with non-negative values.

Using getters and setters, you can implement additional logic or validations to ensure data integrity and control how properties are accessed and modified. This allows you to create more robust and flexible LWC components while maintaining encapsulation and abstraction.


 Interviewer: What is the role of the `lightning-datatable` component in LWC?


 Interviewee: The `lightning-datatable` component is used to display tabular data in a customizable and user-friendly format. Here's an example:





// datatableExample.js
import { LightningElement } from 'lwc';

export default class DatatableExample extends LightningElement {
    data = [
        { Id: '001', Name: 'Account 1', Industry: 'Finance' },
        { Id: '002', Name: 'Account 2', Industry: 'Technology' },
        { Id: '003', Name: 'Account 3', Industry: 'Healthcare' },
    ];

    columns = [
        { label: 'Account Name', fieldName: 'Name', type: 'text' },
        { label: 'Industry', fieldName: 'Industry', type: 'text' },
    ];
}

 Interviewer: How can you use pub-sub (publish-subscribe) pattern in LWC to communicate between unrelated components?

 Interviewee: To implement the pub-sub (publish-subscribe) pattern in LWC to facilitate communication between unrelated components, you can create a centralized service that handles the event subscription and publishing. This service acts as a mediator, allowing components to communicate without having direct references to each other.

Here's a step-by-step guide on how to use the pub-sub pattern in LWC:

Step 1: Create the Pub-Sub Service

Create a separate JavaScript file for the pub-sub service. This service will provide functions for subscribing to events and publishing events.

// pubSubService.js

const eventListeners = {};

export function subscribe(eventName, callback) {
  if (!eventListeners[eventName]) {
    eventListeners[eventName] = [];
  }
  eventListeners[eventName].push(callback);
}

export function publish(eventName, payload) {
  if (eventListeners[eventName]) {
    eventListeners[eventName].forEach(callback => callback(payload));
  }
}

Step 2: Implement Subscription in the Receiving Component

In the component that needs to receive the event, import the `subscribe` function from the pub-sub service and use it to listen for the specific event.

// receiverComponent.js
import { LightningElement } from 'lwc';
import { subscribe } from 'c/pubSubService';

export default class ReceiverComponent extends LightningElement {
  connectedCallback() {
    subscribe('eventName', this.handleEvent);
  }

  handleEvent(payload) {
    // Handle the received event data (payload)
    console.log('Received payload:', payload);
  }
}

Step 3: Implement Publishing in the Sending Component

In the component that needs to send the event, import the `publish` function from the pub-sub service and use it to publish the event with optional data (payload).

// senderComponent.js
import { LightningElement } from 'lwc';
import { publish } from 'c/pubSubService';

export default class SenderComponent extends LightningElement {
  handleClick() {
    const eventData = { message: 'Hello from sender!' };
    publish('eventName', eventData);
  }
}

Step 4: Verify the Communication

When the `handleClick` method in the `SenderComponent` is called, it publishes the 'eventName' event along with the `eventData`. The `ReceiverComponent` is already subscribed to the 'eventName' event, so its `handleEvent` method will be triggered, and it will log the received payload in the console.

Using the pub-sub pattern, the `SenderComponent` and `ReceiverComponent` do not need to be directly related or know about each other. The communication between them is achieved through the centralized `pubSubService`, which acts as an intermediary for passing events and data between unrelated components.

This pattern is beneficial when you have components that are not directly connected in the component hierarchy but still need to communicate with each other. It promotes decoupling and makes the application more maintainable and scalable.


Scenario-based LWC Interview Questions


Scenario 1 :
You have a Lightning web component that needs to fetch data from an external API. How would you approach this in LWC?

Answer: In this scenario, I would use the `@wire` decorator in LWC to fetch data from the external API. The `@wire` decorator allows for reactive data fetching and synchronization with the Salesforce backend. I would create a wire adapter function that makes the API call and retrieves the data. Then, I would decorate a property in the component with `@wire` and pass the wire adapter function as the parameter. The component will automatically receive and update the property with the data from the API.

Example Code : javascript

import { LightningElement, wire } from 'lwc';
import { fetchDataFromAPI } from 'my/wireAdapter';

export default class MyComponent extends LightningElement {
  @wire(fetchDataFromAPI)
  data;
}

Explanation: In the example code above, the `fetchDataFromAPI` wire adapter function is called to fetch `data` from the external API. The data property is decorated with `@wire` and automatically receives and updates the data from the wire adapter.


Scenario 2 :
You need to conditionally render a section of your Lightning web component based on a Boolean value. How would you achieve this in LWC?

Answer: To conditionally render a section of a Lightning web component in LWC, you can use an `if:true` directive along with the Boolean value. Wrap the section that needs to be conditionally rendered with an HTML template element and apply the `if:true` directive to it, binding it to the Boolean property. When the Boolean value is true, the section will be rendered, and when it is false, the section will be hidden.

Example Code : html

Explanation: In the example code above, the `showSection` Boolean property is used with the `if:true` directive to conditionally render the section inside the template. When `showSection` is true, the section will be rendered, and when it is false, the section will not be displayed.


Scenario 3 :
You want to display a list of records in a Lightning web component. How would you iterate over the records and render them in LWC?

Answer: To display a list of records in LWC, you can use the `for:each` directive along with an iterator variable. Iterate over the list of records and bind the iterator variable to each item in the list. Then, use the iterator variable inside the template to render the data for each record.

Example Code : html

Explanation: In the example code above, the `for:each` directive is used to iterate over the `records` list. The iterator variable `record` represents each item in the list, and the key attribute is set to the record's unique identifier (`Id `in this case). The `Name` field of each record is rendered inside the list item (`li`).


Scenario 4 :
You need to pass data from a parent component to a child component in LWC. How would you achieve this?

Answer: To pass data from a parent component to a child component in LWC, you can use component properties. Define a property in the child component using the `@api` decorator. Then, in the parent component's template, bind the desired value to the child component's property using attribute syntax.

Parent Component:

Example Code : html

Child Component:

javascript

import { LightningElement, api } from 'lwc';

export default class ChildComponent extends LightningElement {
  @api message;
}

Explanation: In the example code above, the `message` property is defined in the child component using the `@api `decorator, making it accessible to the parent component. The parent component binds the `parentMessage` value to the child component's `message `property using attribute syntax (`message={parentMessage}`).


Scenario 5 :
You want to handle an event fired from a child component in a parent component. How would you achieve this in LWC?

Answer: To handle an event fired from a child component in a parent component in LWC, you can use event handling and event propagation. In the child component, define a custom event using the `CustomEvent` constructor and dispatch it using the `dispatchEvent` method. In the parent component, use the `on` directive to listen for the custom event and handle it with a JavaScript method.

Child Component:

Example Code : javascript

// Dispatching the custom event
const customEvent = new CustomEvent('myevent', { detail: { data: 'Event data' } });
this.dispatchEvent(customEvent);

Parent Component:

html

javascript

import { LightningElement } from 'lwc';

export default class ParentComponent extends LightningElement {
  handleEvent(event) {
    const eventData = event.detail.data;
    // Handle the event data
  }
}

Explanation: In the example code above, the child component dispatches a custom event named `myevent` with some data. In the parent component, the `onmyevent` directive is used to listen for the custom event and invoke the `handleEvent` method. The event data can be accessed from the `event.detail` property.


Scenario 6 :
You want to show a toast message in LWC. How would you achieve this?

Answer: To show a toast message in LWC, you can use the `ShowToastEvent` from the Lightning Messaging Service. Import the `ShowToastEvent` from `lightning/platformShowToastEvent` module and create a new instance of it with the desired parameters. Dispatch the toast event using the `dispatchEvent` method to display the toast message.

Example Code : javascript

import { LightningElement } from 'lwc';
import { ShowToastEvent } from 'lightning/platformShowToastEvent';

export default class MyComponent extends LightningElement {
  showToast() {
    const toastEvent = new ShowToastEvent({
      title: 'Success',
      message: 'Toast message',
      variant: 'success',
    });
    this.dispatchEvent(toastEvent);
  }
}

Explanation: In the example code above, the `showToast` method creates a new instance of the `ShowToastEvent` with a title, message, and variant. The `dispatchEvent` method is used to dispatch the toast event and display the toast message with the specified details.


Scenario 7 :
You need to navigate to a specific record in LWC. How would you achieve this?

Answer: To navigate to a specific record in LWC, you can use the `NavigationMixin` provided by the Lightning Web Components. Import the `NavigationMixin` and use it to navigate to the desired record by specifying the record's Id or a URL.

Example Code : javascript

import { LightningElement, wire } from 'lwc';
import { NavigationMixin } from 'lightning/navigation';

export default class MyComponent extends NavigationMixin(LightningElement) {
  navigateToRecord(recordId) {
    this[NavigationMixin.Navigate]({
      type: 'standard__recordPage',
      attributes: {
        recordId: recordId,
        actionName: 'view',
      },
    });
  }
}

Explanation: In the example code above, the `navigateToRecord` method uses the `NavigationMixin` to navigate to a specific record. The `type` property is set to `'standard__recordPage'` to navigate to a record page, and the `recordId` attribute is specified to indicate the record's Id. The `actionName` is set to `'view'` to open the record in view mode.


Scenario 8 :
Implement a custom LWC component to display a list of accounts fetched from an Apex method.

Answer: Sure! Let's implement a custom LWC (Lightning Web Component) to display a list of accounts fetched from an Apex method.

HTML Markup (accountList.html):

JavaScript (accountList.js):

import { LightningElement, wire, track } from 'lwc';
import getAccounts from '@salesforce/apex/AccountController.getAccounts';

export default class AccountList extends LightningElement {
    @track accounts;

    @wire(getAccounts)
    wiredAccounts({ error, data }) {
        if (data) {
            this.accounts = data;
        } else if (error) {
            // Handle error if needed
            console.error('Error fetching accounts:', error);
        }
    }
}

Apex (AccountController.cls):

public with sharing class AccountController {
    @AuraEnabled(cacheable=true)
    public static List getAccounts() {
        return [SELECT Id, Name, Phone, BillingCity, BillingCountry FROM Account];
    }
}

Explanation: In the `accountList.html` file, we use a Lightning Card to display the list of accounts. The list of accounts is shown using a Lightning Layout with a Lightning Layout Item for each account.

The `@wire` decorator in the `accountList.js` file is used to call the `getAccounts` method from the Apex controller and fetch the list of accounts. The response is stored in the `accounts` property, which is tracked, so any changes in the data will automatically update the UI.

The `getAccounts` method in the `AccountController.cls` Apex class fetches the list of accounts from the database using a SOQL query and returns the result.

To use this LWC component, add it to the appropriate page or component where you want to display the list of accounts. When the component is loaded, it will automatically fetch the accounts from the Apex method and display them in the UI. If there are any errors while fetching the data, the error will be logged to the browser console for debugging purposes.


These were important LWC interview questions with detailed answers, examples, and explanations. Good luck with your interview!

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About The Author

Hey, my name is Saurabh Samir and I am Salesforce Developer. I have been helping to elevate your Salesforce Knowledge. Do comment below if you have any questions or feedback's.