👨‍💼 Interviewer:

Let’s start simple.
Can you explain lifecycle hooks in LWC and how they behave with parent and child components?

👨‍💻 You (Ideal Answer):

Lifecycle hooks are methods that run at different stages of a component’s life, such as creation, rendering, and removal.

The key hooks are constructor, connectedCallback, renderedCallback, and disconnectedCallback.

In parent-child scenarios, the parent initializes first, but the child finishes rendering first. The execution order is:

Parent constructor 
→ Parent connectedCallback 
→ Child constructor 
→ Child connectedCallback 
→ Child renderedCallback 
→ Parent renderedCallback
    

This is important because if I need to access a child component, I should use renderedCallback().

👨‍💼 Interviewer:

Good.
Have you faced any lifecycle-related issues in real projects?

👨‍💻 You (Ideal Answer):

Yes, one common issue I faced was calling a child component’s method inside connectedCallback().

The problem was that the child component was not yet rendered at that stage, so the reference was null, and the method call failed.

I fixed this by moving the logic to renderedCallback(), where the DOM is fully available.

To avoid repeated execution (since renderedCallback() runs multiple times), I added a guard condition:

isRendered = false;

renderedCallback() {
    if (this.isRendered) return;

    this.isRendered = true;

    const child = this.template.querySelector('c-child-component');
    if (child) {
        child.someMethod();
    }
}
    

This ensured the logic runs only once and avoids unnecessary re-render issues.

👨‍💼 Interviewer:

Nice.
What is the difference between @wire and imperative Apex?

👨‍💻 You (Ideal Answer):

The main difference is how the Apex method is executed and controlled.

@wire is reactive and automatically executed by the framework whenever its parameters change. It is mainly used for read-only operations and works well with caching.

On the other hand, imperative Apex is manually invoked from JavaScript, giving full control over when and how the method is executed.

In real scenarios, I use @wire when data needs to load automatically or depends on reactive parameters.

I use imperative Apex when I need control over execution, such as handling button clicks, performing DML operations, or managing complex logic.

// @wire (automatic execution)
@wire(getAccounts) accounts;

// Imperative (manual execution)
getAccounts()
  .then(result => {
    this.accounts = result;
  });
    

So, in short, @wire is reactive and automatic, while imperative Apex is controlled and flexible.

👨‍💼 Interviewer:

Good explanation.
If I want to call Apex only on button click, can I use @wire?

👨‍💻 You (Ideal Answer):

Not directly. Since @wire is reactive, it executes automatically when its parameters change, not on demand like a button click.

However, we can control its execution indirectly using a reactive parameter (trigger variable).

In this approach, I use one variable for input and another variable as a trigger. When the button is clicked, I update the trigger variable, which causes the @wire method to execute.

// Reactive trigger variable
triggerKey = null;

// Wire method
@wire(getAccounts, { key: '$triggerKey' })
wiredAccounts({ data, error }) {
    if (data) {
        this.accounts = data;
    }
}

// Button click handler
handleClick() {
    this.triggerKey = Date.now(); // changing value triggers @wire
}
    

This way, I can control when @wire runs, but for full control and better readability, I usually prefer imperative Apex for button-driven actions.