Top 20+ LWC Interview Questions and Answers

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Lightning Web Components (LWC) is a modern web framework by Salesforce. It was launched in 2019 to replace the older Aura framework. LWC uses standard JavaScript and HTML, which makes it faster and easier to use. Philippe Ozil and other Salesforce engineers helped build it. Many companies now prefer LWC for building Salesforce apps. That’s why interviewers ask more questions about it. In this blog, you will find 20+ common LWC interview questions with simple answers to help you get ready.

Basic LWC Interview Questions

Here are some common LWC basic interview questions that beginners are often asked during Salesforce developer interviews.

1. What is Lightning Web Components (LWC) and how is it different from Aura Components?

LWC is a modern web framework built by Salesforce in 2019. It uses standard HTML, CSS, and JavaScript. Unlike Aura, it doesn’t rely on a proprietary model. LWC is faster, simpler, and closer to native web development.

2. What are the key files required to create an LWC component?

Every LWC component has three main files –

• .html for the template
• .js for logic
• .js-meta.xml for configuration

All are required.

3. How do you bind data from JavaScript to HTML in LWC?

Use curly braces {} in the HTML to bind public or tracked properties from the JavaScript file.

4. What is the role of @track in LWC?

@track makes a property reactive. If its value changes, the UI updates automatically. It’s used for internal state.

5. Can we use Lightning Data Service in LWC? How?

Yes, you can use lightning-record-form, lightning-record-view-form, or wire adapters like getRecord to fetch data.

LWC Interview Questions for Freshers

These LWC interview questions and answers are perfect for freshers starting their journey with Salesforce and Lightning Web Components.

6. How do you pass data from parent to child component in LWC?

Use the @api decorator in the child component’s JavaScript file. Then pass the value as an HTML attribute from the parent. The child receives it as a public property.

7. What is the difference between @api and @track in LWC?

@api is used to make a property public so that parent components can pass data to it.
@track is used to make private properties reactive. It updates the UI when internal values change.

8. What is the purpose of template in LWC HTML files?

The <template> tag wraps all HTML in the component. It defines what gets rendered on the page. Without it, the component won’t work.

9. How can you create a simple input form using LWC?

I use standard HTML tags like <lightning-input> inside the template. Then I bind the input to properties in the JavaScript file. On submit, I handle the values and reset the form if needed.

10. How do you handle button click events in LWC?

Add the onclick event in the HTML and call a method in the JavaScript file.

For example:

<lightning-button label=”Click Me” onclick={handleClick}></lightning-button>

Then write a handleClick() function in the JS file to handle the event.

LWC Interview Questions for Experienced

Let’s go through some advanced salesforce LWC interview questions and answers for experienced professionals to help you prepare better.

11. How do you communicate between unrelated LWC components?

For unrelated components, I use Lightning Message Service (LMS). It lets components publish and subscribe to messages across the app. I define a message channel and use publish() and subscribe() functions from the lightning/messageService.

12. What are the limitations of using wire service in LWC?

The wire service is reactive but not flexible for all cases. You can’t call it inside a function or conditionally. It automatically runs when its parameters change, which can sometimes cause unnecessary Apex calls.

13. How do you handle large data sets or pagination in LWC?

I prefer using server-side pagination. Instead of loading everything at once, I fetch a limited number of records per request. I send page number and size to Apex and update the UI on response. This keeps the component fast.

14. What are reactive properties and how do they work in LWC?

Reactive properties in LWC update the UI when their value changes. Any property decorated with @track, @api, or used with @wire becomes reactive. This means the UI reflects changes automatically without extra steps.

15. How do you implement modal popups in LWC?

I create a boolean variable like isModalOpen. Then I show or hide a <section> with if:true={isModalOpen}. I also add CSS to style it like a modal. I handle open and close actions using button click events.

Also Read - Top 25+ Apex Interview Questions and Answers

LWC Advanced Interview Questions

This section covers complex salesforce LWC interview questions often asked in senior-level Salesforce developer interviews.

16. How do you optimize performance in large LWC applications?

I avoid unnecessary Apex calls and fetch only required fields. I use pagination, lazy loading, and memoization with @wire. Caching data wherever possible also helps reduce repeated processing. I keep component logic lean and reusable.

17. Explain the concept of Shadow DOM in the context of LWC.

Shadow DOM provides a layer of encapsulation. It keeps a component’s styles and structure separate from the main DOM. In LWC, this isolation protects components from outside CSS and prevents conflicts between elements.

18. How do you debug LWC components in the browser?

I use browser DevTools. I open the Sources tab to set breakpoints in the .js file. Console logs also help trace values. The Lightning Web Components extension for Chrome is useful to inspect component structure and state.

19. What are the differences between imperative and reactive Apex calls?

Reactive calls use the @wire decorator and auto-run when parameters change. They are useful for simple, repeated fetches.
Imperative calls use regular functions and run only when triggered – great for custom logic like button clicks or form submissions.

LWC Scenario Based Interview Questions

Here are some real-world salesforce LWC interview questions designed to test your practical understanding and problem-solving skills.

20. You need to display a dynamic list and allow users to edit each row. How would you approach this in LWC?

I use a <lightning-datatable> with editable columns. I bind the list to a tracked property. When users make changes, I handle the onsave event and update the data in JavaScript or send it to Apex.

21. How would you handle form validation with custom error messages in LWC?

I check each field using simple JavaScript before submitting. For <lightning-input>, I use setCustomValidity() to show specific error messages, then call reportValidity() to trigger the error display. This keeps the user informed about what went wrong.

22. How do you handle a situation where multiple child components need to notify a parent about different events?

Each child fires a custom event with a unique event name. In the parent component, I add different handlers for each child event. This way, the parent can respond based on which child sent the data and what action was triggered.

Also Read - Top 15+ Salesforce Interview Questions On Triggers

LWC Coding Interview Questions

These hands-on LWC interview questions focus on coding skills and are commonly asked during technical rounds.

23. Write a simple LWC component that fetches Account records using Apex and displays them in a table.

Tests: Apex integration, wire service, lightning-datatable.

Apex Class:

public with sharing class AccountController {

    @AuraEnabled(cacheable=true)

    public static List<Account> getAccounts() {

        return [SELECT Id, Name, Industry FROM Account LIMIT 10];

    }

}

JS File:

import { LightningElement, wire } from ‘lwc’;

import getAccounts from ‘@salesforce/apex/AccountController.getAccounts’;

export default class AccountTable extends LightningElement {

    @wire(getAccounts) accounts;

    columns = [

        { label: ‘Name’, fieldName: ‘Name’ },

        { label: ‘Industry’, fieldName: ‘Industry’ }

    ];

}

HTML File:

<template>

    <lightning-datatable

        data={accounts.data}

        columns={columns}

        key-field=”Id”>

    </lightning-datatable>

</template>

24. Create a component that takes user input and calculates a live result on the screen.

Tests: Event handling, reactive property, data binding.

JS File:

import { LightningElement } from ‘lwc’;

export default class LiveCalculator extends LightningElement {

    inputVal = 0;

    get result() {

        return this.inputVal * 2;

    }

    handleChange(event) {

        this.inputVal = Number(event.target.value);

    }

}

HTML File:

<template>

    <lightning-input label=”Enter number” onchange={handleChange}></lightning-input>

    <p>Double: {result}</p>

</template>

25. Write LWC code to toggle visibility of a section when a button is clicked.

Tests: Conditional rendering, boolean toggle, UI handling.

JS File:

import { LightningElement } from ‘lwc’;

export default class ToggleSection extends LightningElement {

    showSection = false;

    toggle() {

        this.showSection = !this.showSection;

    }

}

HTML File:

<template>

    <lightning-button label=”Toggle” onclick={toggle}></lightning-button>

    <template if:true={showSection}>

        <p>This section is visible</p>

    </template>

</template>

26. How do you write unit tests for an LWC component using Jest?

Tests: Component rendering, DOM checking, basic Jest setup.

Component (myComponent.js):

import { LightningElement } from ‘lwc’;

export default class MyComponent extends LightningElement {

    message = ‘Hello’;

}

Test File (myComponent.test.js):

import { createElement } from ‘lwc’;

import MyComponent from ‘c/myComponent’;

describe(‘c-my-component’, () => {

    it(‘displays default message’, () => {

        const element = createElement(‘c-my-component’, {

            is: MyComponent

        });

        document.body.appendChild(element);

        const p = element.shadowRoot.querySelector(‘p’);

        expect(p.textContent).toBe(‘Hello’);

    });

});

Also Read - Top 20+ Salesforce Integration Interview Questions

Other Important Salesforce LWC Interview Questions

This section highlights additional salesforce LWC interview questions that you shouldn’t miss while preparing for your interview.

Salesforce Developer LWC Interview Questions

1. How do you handle record creation and updates using Apex in LWC?
2. What is the use of Lightning Message Service (LMS)?
3. How do you deploy LWC components to different orgs using SFDX?
4. How do you handle CRUD operations securely in LWC?

LWC Lifecycle Hooks Interview Questions

1. What is the order of lifecycle hooks in LWC?
2. Can you call Apex methods inside connectedCallback()?
3. What happens if an error occurs in a lifecycle hook?
4. How can you use lifecycle hooks to fetch data on load?

LWC Components Interview Questions

1. How do you create reusable components in LWC?
2. How does conditional rendering work in LWC?
3. What are slots in LWC and how are they used?
4. How do you pass events from child to parent component in LWC?

Also Read - Top 20+ Salesforce Testing Interview Questions and Answers

Tips to Prepare for Salesforce LWC Interview Questions

Here are some practical tips to help you prepare for your upcoming Salesforce LWC interview. 

• Revise the core concepts of JavaScript, especially ES6+ features.
• Practice writing LWC components from scratch, not just reading code.
• Understand when to use @api, @track, and @wire.
• Go through official Salesforce docs and Trailhead modules.
• Practice explaining your code during mock interviews.

Also Read - Top 25+ Salesforce Developer Interview Questions and Answers

Wrapping Up

These 20+ LWC interview questions and answers are meant to help you understand what interviewers actually ask. From basic concepts to advanced coding – each question gives you a clear idea of what to expect. 

Looking for LWC jobs in India? Visit Hirist – a trusted job portal for IT professionals. Here, you can find the latest and best LWC opportunities across top companies.

Also Read - Top 30+ Salesforce Interview Questions and Answers

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