LWC Interview Question – Part 2

Certainly! Here's a mix of Lightning Web Component (LWC) interview questions suitable for both freshers and experienced developers: 

  1. What are the different types of data binding in LWC?

There are two main types of data binding in LWC: 

  • One-Way Data Binding: In one-way data binding, you can bind a property in your JavaScript controller to an element or attribute in the template. Changes in the JavaScript property update the template. 
  • Two-Way Data Binding: Two-way data binding is a combination of one-way data binding and user input handling. You can use it with input elements like input, textarea, or select to automatically update the JavaScript property when the user interacts with the input field, and vice versa. 
  1. How can you handle events in LWC components?

 In LWC, you can handle events using event listeners in the template. For example, you can use onchange, onclick, or other event handlers to respond to user interactions. You can also create custom events using the CustomEvent constructor in JavaScript and dispatch them to communicate between components. 

  1. What is the difference between a wire adapter and an imperative Apex call in LWC?
  • Wire Adapter: Wire adapters are used to fetch data from Salesforce and are reactive by nature. They automatically re-fetch data when relevant changes occur, and they use the @wire decorator. Wire adapters are ideal for data binding and displaying real-time data. 
  • Imperative Apex Call: Imperative Apex calls are used when you need to fetch data or invoke server-side actions based on specific events or conditions. These calls are made imperatively using JavaScript methods and are not automatically reactive like wire adapters. You manually invoke them when needed.  
  1. What are decorators in LWC, and how do they work?

Decorators in LWC are special JavaScript annotations that provide metadata about properties, methods, or fields in a component. They are used to define the behavior of those properties or methods. For example, @api exposes a property as public, @wire establishes a wire adapter, and @track marks a property as reactive. 

  1. What is the role of the @track, @wire, & @Api decorator in LWC, and when should you use it?
  • @track: The @track decorator marks a property as reactive. It allows the property to re-render the template when its value changes. Use it for properties that you want to make reactive. 
  • @wire: The @wire decorator is used to call a wire adapter to fetch data from Salesforce. It's suitable for data binding and displaying real-time data. 
  • @api: The @api decorator exposes a property as public, allowing it to be accessible in parent components. Use it when you want to pass data to or from a parent component. 
  1. How do you handle errors and exceptions in LWC components?

To handle errors and exceptions in LWC components, you can use try-catch blocks or use the try-catch construct in JavaScript. You can catch errors and display error messages in the template or log them for debugging purposes. 

  1. How can you communicate between components in LWC?

We can communicate between components in LWC using several methods, including: 

  • Events: You can dispatch custom events from child components and handle them in parent components. 
  • @api Decorator: You can expose properties or methods in child components and access them in parent components. 
  • Lightning Message Service: You can use this service to communicate between components in different parts of the application. 

dont miss out iconDon't forget to check out: Understanding Decorators and Lifecycle Hooks in Lightning Web Components (LWC)

  1. Explain the concept of shadow DOM in LWC.

Shadow DOM is a web standard that encapsulates the styles and structure of a component, preventing them from affecting or being affected by the styles and structure of other components on the page. In LWC, each component has its own shadow DOM, which enhances encapsulation and reusability. 

  1. How can we pass data from a parent component to a child component in LWC?

Data can be passed from a parent component to a child component in LWC by using public properties. You decorate a property in the child component with @api to make it public, and then you set its value in the parent component's template when including the child component. The child component can access this data via the decorated property. 

  1. Describe the differences between client-side and server-side controllers in LWC.
  • Client-Side Controllers (JavaScript): Client-side controllers are used for handling events, data processing, and logic on the client side (browser). They are written in JavaScript and run within the user's browser, making them suitable for handling user interactions and local data manipulation. 
  • Server-Side Controllers (Apex): Server-side controllers are used for making server calls to Salesforce's servers. They are written in Apex (Salesforce's server-side language) and are responsible for performing complex server-side operations, such as querying or modifying Salesforce data. 
  1. How do you integrate LWC components with Apex methods?

To integrate LWC components with Apex methods, you can use the @wire decorator to call Apex methods imperatively. You define a JavaScript method with @wire and provide the Apex method's name and parameters. The data returned from Apex is automatically cached and re-fetched when needed. 

  1. Explain the difference between reactive and non-reactive properties in LWC.
  • Reactive Properties: Reactive properties are marked with the @track decorator in LWC. Changes to these properties trigger re-rendering of the template, making them suitable for properties you want to make reactive to changes. 
  • Non-Reactive Properties: Non-reactive properties are not marked with @track. Changes to these properties do not automatically trigger the re-rendering of the template. You typically use non-reactive properties for values that don't need to be reactive. 
  1. Describe the concept of data binding in LWC.

Data binding in LWC is the process of connecting properties in the JavaScript controller with elements or attributes in the HTML template. It allows you to reflect changes in the JavaScript properties immediately in the template, and vice versa. Data binding can be one-way or two-way. 

  1. How can you implement error handling and validation in LWC forms?

Error handling and validation in LWC forms can be implemented by performing client-side validation using JavaScript. You can use JavaScript to validate user input, display error messages in the template, and prevent form submission when validation fails. 

  1. Describe the concept of two-way data binding in LWC.

Two-way data binding in LWC allows you to automatically synchronize changes between an input element and a JavaScript property. It's commonly used with input fields like input, textarea, and select. When the user interacts with the input field, changes are automatically reflected in the associated JavaScript property, and vice versa. 

  1. Explain when you would use the connectedCallback lifecycle hook.

The connectedCallback lifecycle hook is used when you need to perform actions when a component is inserted into the DOM (document object model) or connected to the view hierarchy. It's often used for initial setup or for actions that should occur once the component is rendered. 

  1. Explain the concept of reactive properties in LWC.

Reactive properties in LWC are properties that are marked with the @track decorator. When a property is marked as reactive, changes to that property trigger a re-render of the component's template, ensuring that the UI reflects the updated property value. 

  1. What tools and resources are typically used for LWC development?

Common tools and resources for LWC development include: 

  • Salesforce Developer Console 
  • Visual Studio Code with Salesforce Extensions 
  • Salesforce Lightning Studio 
  • Lightning Design System (SLDS) for styling 
  • Salesforce Developer Documentation 
  1. How does LWC differ from Aura?

LWC and Aura are both component-based frameworks used in Salesforce, but there are key differences: 

  • LWC is based on modern web standards and uses a Shadow DOM for encapsulation, whereas Aura relies on its own component model. 
  • LWC has better performance due to its fine-grained rendering control. 
  • LWC components can be used in standalone apps outside of Salesforce, while Aura is specific to the Salesforce platform. 
  • LWC enforces stricter security via the Lightning Locker Service. 

dont miss out iconCheck out another amazing blog by Salesforce Learners here: The Impact of Salesforce Certification on Your Salesforce Career

  1. How do you fetch data from a Salesforce object in LWC?

You can fetch data from a Salesforce object in LWC by using wire adapters or imperative Apex calls. Wire adapters are typically used for reactive data binding, while imperative Apex calls are used for custom data retrieval. You decorate a property with the @wire decorator to automatically retrieve data from Salesforce based on a specified wire adapter or call Apex methods imperatively using JavaScript. 


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