LWC Interview Questions - Part 1

Important Questions

Question 1: What is the basic structure of a Lightning Web Component in LWC?

Answer: The basic structure of a Lightning Web Component in LWC consists of a JavaScript class, an HTML template, and a metadata configuration file (XML). The JavaScript class contains the component's logic, the HTML template defines the component's structure, and the metadata file specifies the component's configuration.

Question 2: How do you create a Lightning Web Component in Salesforce?

Answer: To create a Lightning Web Component in Salesforce, you can use the Salesforce CLI (Command-Line Interface) or the Salesforce Developer Console. With the CLI, you can use the force:lightning:component:create command, while in the Developer Console, you can create a new Lightning Web Component file and its associated metadata.

Question 3: What is the difference between LWC and Aura components in Salesforce?

Answer: LWC is the latest component framework introduced by Salesforce, while Aura components are the older framework. LWC offers better performance, easier debugging, and a more modern programming model compared to Aura components. LWC uses standard HTML and JavaScript, whereas Aura components use a proprietary component markup language.

Question 4: How do you pass data from a parent component to a child component in LWC?

Answer: To pass data from a parent component to a child component in LWC, you can use component properties. The parent component can set values for the properties in the child component's HTML template or JavaScript file, and the child component can access those values using the @api decorator.

Question 5: How can you handle events in Lightning Web Components?

Answer: In LWC, you can handle events using event handlers and the on attribute. You can define event handlers in the JavaScript file of a component and associate them with specific events in the component's HTML template. The on attribute allows you to specify which event should trigger a particular event handler.

Don't forget to check out: Decorators in LWC | Salesforce Developer Guide

Question 6: What is the role of the wire service in LWC? How do you use it to fetch data from Salesforce?

Answer: The wire service in LWC is used for fetching data from Salesforce without writing Apex code. It simplifies the process of retrieving and caching data by providing a reactive data binding approach. You can use the wire service to call Apex methods, get data from Salesforce objects, or invoke external services.

Question 7: What are the lifecycle hooks available in LWC? Explain each one.

Answer: LWC provides several lifecycle hooks that allow you to perform actions at specific points during the component's lifecycle. The available lifecycle hooks are: constructor, connectedCallback, renderedCallback, disconnectedCallback, errorCallback, and render(). Each hook serves a specific purpose, such as initializing data, performing DOM manipulation, handling errors, and more.

Question 8: How do you communicate between sibling components in LWC?

Answer: To communicate between sibling components in LWC, you can use a pub-sub (publish-subscribe) pattern. This involves creating a shared service component that acts as a communication hub. Sibling components can publish events to the hub, and other sibling components can subscribe to those events to receive and react to the data.

Question 9: What are the best practices for writing efficient and reusable Lightning Web Components?

Answer: Some best practices for writing efficient and reusable Lightning Web Components include optimizing rendering performance, using the wire service for data retrieval, leveraging component composition, adopting a modular approach, writing clean and maintainable code, and following Salesforce's security and accessibility guidelines.

Question 10: How can you invoke Apex methods from a Lightning Web Component?

Answer: You can invoke Apex methods from a Lightning Web Component using the @wire decorator or by calling the Apex methods imperatively. The @wire decorator enables declarative data binding between Apex methods and component properties. Imperative calls use the import statement to import the Apex class and then invoke the methods directly.

Question 11: How do you handle errors and display error messages in LWC?

Answer: In LWC, you can handle errors using the try...catch block or by implementing the errorCallback lifecycle hook. When an error occurs, you can catch it and handle it appropriately, such as displaying an error message on the component or logging the error for debugging purposes.

Question 12: What is the role of the Lightning Data Service in LWC? How do you use it?

Answer: The Lightning Data Service in LWC provides a standard way to interact with Salesforce data. It abstracts the underlying data access and manipulation operations, allowing you to work with records, perform CRUD operations, handle record changes, and leverage standard Salesforce user interfaces without writing Apex code.

Question 13: How can you implement pagination in LWC?

Answer: Pagination in LWC can be implemented by using the lightning-datatable component and its attributes such as offset and limit. By managing the offset and limit values based on user interactions, you can fetch and display a subset of data at a time, providing a paginated experience to the users.

Question 14: How do you handle client-side caching in LWC?

Answer: LWC provides client-side caching out of the box for wire service calls. By using the @wire decorator with the { cacheable: true } configuration, the response data from a wire service call is automatically cached in the client's browser. Subsequent requests for the same data can be served from the cache, improving performance.

Question 15: What are the different ways to style a Lightning Web Component?

Answer: You can style a Lightning Web Component using CSS. LWC supports inline styles, style sheets, and CSS classes. Inline styles allow you to apply styles directly to HTML elements using the style attribute. Style sheets can be included in the component's CSS file, and CSS classes can be defined and applied to HTML elements to achieve consistent styling.

Question 16: How do you pass data from a child component to a parent component in LWC?

Answer: To pass data from a child component to a parent component in LWC, you can use custom events. The child component can fire a custom event with the data payload, and the parent component can handle that event using an event handler method. The data can be accessed in the parent component's event handler method.

Question 17: What is the role of the track decorator in LWC? How does it work?

Answer: The track decorator is used to create reactive properties in LWC. It enables change tracking for the decorated property, allowing the framework to detect changes and update the component's rendering accordingly. By using track, you can optimize performance and ensure that only the necessary parts of the component are rerendered when a property value changes.

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Question 18: How do you handle user input and form submissions in LWC?

Answer: In LWC, you can handle user input and form submissions by using event handlers and two-way data binding. By binding input fields to component properties using @track or @api, you can capture user input. You can then use event handlers like onchange or onsubmit to listen for user actions and invoke appropriate methods to handle the input or form submission logic.

Question 19: What are the different ways to communicate between LWC and Aura components?

Answer: LWC and Aura components can communicate with each other using events, whether it's component events, application events, or platform events. Both LWC and Aura components can fire and handle events, allowing them to exchange data and trigger actions across the component framework boundaries.

Question 20: How can you dynamically create and destroy components in LWC?

Answer: In LWC, you can dynamically create and destroy components using the lightning:dynamicComponent component or by manipulating the component's DOM. The lightning:dynamicComponent allows you to create components dynamically based on the provided component type and attributes. Alternatively, you can use JavaScript methods like createElement and removeChild to manage the component's DOM dynamically.

Question 21: What is the role of the get and set methods in LWC?

Answer: The get and set methods in LWC are used for defining and managing reactive properties. The get method retrieves the current value of a property, while the set method sets a new value for the property. By using these methods, you can define custom logic, perform validations, or trigger actions when a property value is accessed or changed.

Question 22: How can you handle user authentication and authorization in LWC?

Answer: User authentication and authorization in LWC can be handled by integrating with Salesforce's identity and access management services. You can use features like OAuth 2.0, JWT (JSON Web Tokens), or SAML (Security Assertion Markup Language) to authenticate users. For authorization, you can leverage Salesforce's sharing rules, permission sets, or custom Apex logic to control access to data and functionality.

Question 23: What is the role of the lightning-navigation the component in LWC?

Answer: The lightning-navigation the component in LWC provides navigation capabilities within Salesforce Lightning Experience. It allows you to navigate to different pages, and record views, and URLs. You can use it to create links, open modals, redirect to different locations, or leverage advanced navigation features like history management and deep linking.

Question 24: How do you handle browser events in LWC?

Answer: In LWC, you can handle browser events by using event handlers in the component's HTML template or JavaScript file. You can bind event handlers to specific HTML elements or components using attributes like onclick, onkeydown, or onchange. By defining event handler methods, you can respond to user actions and interact with the browser's event system.

Question 25: What are the different ways to navigate between components in LWC?

Answer: In LWC, you can navigate between components using the lightning-navigation component, the NavigationMixin mixin, or the window.location object. The lightning-navigation component and NavigationMixin provide more comprehensive navigation features like URL-based navigation, history management, and deep linking, while the window.location object allows basic navigation by modifying the browser's URL.