Lightning Web Components - Basics Create Lightning Web Components

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Questions and Answers

What feature is used to control the rendering of elements based on the loading state in Lightning Web Components?

lwc:display

lwc:switch

lwc:show

lwc:if (correct)

Which JavaScript method is used to perform an action after a component is connected to the DOM?

initComponent

handleLoading

connectedCallback (correct)

setTimeout

How should a component folder be named if the component is referred to as 'myComponent' in markup?

myComponent (correct)

my-component

MyComponent

my_component

What is the purpose of the 'ready' property in the JavaScript snippet provided?

To indicate whether the data has been loaded Signup and view all the answers

Which component is used to visually enhance the representation of the 'material' and 'category' fields in the provided HTML?

lightning-badge Signup and view all the answers

In the context of component names, which naming convention prevents the use of hyphens in folder or file names?

Camel case Signup and view all the answers

What is the correct format for referencing a component with the folder name 'viewSource' in markup?

c-view-source Signup and view all the answers

What material is specified for the bike in the JavaScript class?

Steel Signup and view all the answers

What property of the bike holds its pricing information?

price Signup and view all the answers

How long does the timer set in the connectedCallback function wait before changing the 'ready' state?

3 seconds Signup and view all the answers

What does the export statement in the given code accomplish?

It declares a class that extends the LightningElement class. Signup and view all the answers

Which lifecycle method is invoked when a Lightning Web Component is added to the DOM?

connectedCallback() Signup and view all the answers

Which of the following statements about decorators in Lightning Web Components is true?

@api decorator marks a field as public. Signup and view all the answers

What is a warning you might encounter when using setTimeout() in the connectedCallback() method?

Restricted async operation warning. Signup and view all the answers

What is the behavior of the this keyword within the context of a Lightning Web Component?

It refers to the class instance itself. Signup and view all the answers

What happens after the connectedCallback() method is executed in the provided example?

The ready variable is set to true after 3 seconds. Signup and view all the answers

Which of the following methods is NOT a lifecycle hook in Lightning Web Components?

initializedCallback() Signup and view all the answers

In Lightning Web Components, which import would you use to define a public API property?

import { LightningElement, api } from 'lwc'; Signup and view all the answers

What functionality does the lwc module provide in Lightning Web Components?

It exposes core functionalities for JavaScript in components. Signup and view all the answers

Which statement correctly describes the use of the connectedCallback() method?

It can initiate setup tasks when the component is inserted into the DOM. Signup and view all the answers

What is the purpose of the @api decorator in a Lightning web component?

To allow properties to be accessed by other components. Signup and view all the answers

When should the @track decorator be used in a Lightning web component?

To observe changes in objects or arrays. Signup and view all the answers

What happens when a public property value changes in a Lightning web component?

The framework reacts and rerenders the component. Signup and view all the answers

What is true regarding public fields and properties in a component?

Fields declared with @api are accessible as properties. Signup and view all the answers

What was required prior to Spring '20 for marking fields as reactive?

Using @track on all fields. Signup and view all the answers

What is the primary function of the @wire decorator?

To retrieve and bind data from a Salesforce org. Signup and view all the answers

In the provided code snippet, what is the significance of the 'bike' object?

It contains attributes to be rendered by the bike component. Signup and view all the answers

Which statement is true regarding fields in Lightning web components?

Fields can only be reactive if decorated with @track. Signup and view all the answers

Which tag is essential in every Lightning web component HTML file?

<template> Signup and view all the answers

What is required to work with Lightning web components in Visual Studio Code?

Visual Studio Code with the Salesforce Extension Pack Signup and view all the answers

Which CLI tool is essential for managing Salesforce projects?

Salesforce CLI Signup and view all the answers

What is the first step in creating a Lightning web component in Visual Studio Code?

Select SFDX: Create Project from the Command Palette Signup and view all the answers

What is the purpose of Lifecycle Hooks in a Lightning web component?

To manage the state and response of a component during its lifecycle Signup and view all the answers

Which file must be created to begin building a new Lightning web component?

app.html Signup and view all the answers

What does the command 'SFDX: Create Lightning Web Component' do?

It creates a new Lightning web component structure in the specified folder Signup and view all the answers

After creating a new component, what should you do with the app.html file?

Paste the necessary HTML structure into it Signup and view all the answers

Study Notes

Learning Objectives

Describe the contents of Lightning web component files.
Create JavaScript methods for Lightning web components.
Utilize lifecycle hooks in component JavaScript.

Developing a Lightning Web Component

Build a data display element independent of specific Salesforce objects.
Example: productCard component from the ebikes sample repository.
Use Visual Studio Code with Salesforce extensions to develop Lightning web components.

Setup Requirements

Familiarity with Salesforce DX.
Use Visual Studio Code (VS Code) with the Salesforce Extension Pack.
Install Salesforce CLI.
Complete the Quick Start: Lightning Web Components project for initial setup.

HTML File Structure

All Lightning web component HTML files contain a template tag to define the component structure.
Create a new component using the Command Palette in VS Code, initializing with the project name 'bikeCard'.
In the component HTML, bind data fields using identifiers in curly braces {}.

JavaScript File Structure

Import necessary modules using import { LightningElement } from 'lwc';.
Define class properties such as name, description, category, material, and price.
Implement a loading state using a boolean variable (e.g., ready) and a timeout function in the connectedCallback() lifecycle hook.

Conditional Rendering

Use lwc:if and lwc:else directives in HTML to control visual elements based on the component state.
Introduce a simulated data load with a timeout to display loading indicators.

Base Lightning Web Components

Leverage base components from the Salesforce Component Reference for easier development.
Example: Use lightning-badge to display properties like material and category as visual badges.

Component Naming Conventions

Components require a folder and files with the same name for automatic linking.
Avoid hyphens in file/folder names; instead, use camel case (e.g., myComponent).

Working with JavaScript

JavaScript methods handle data, events, and state changes in Lightning web components.
The base class for components is LightningElement, providing lifecycle hooks and functionality.

Lifecycle Hooks

Lifecycle hooks allow interaction with component lifecycle events (created, added to the DOM, rendered, errors, removed).
connectedCallback() executes when a component is inserted into the DOM.

Decorators in Lightning Web Components

@api: Marks properties as public, making them accessible to parent components.
@track: Observes changes to object properties or array elements, triggering re-renders. (Note: Only necessary for properties of objects/arrays; all fields are reactive otherwise).
@wire: Simplifies data fetching from Salesforce.

Example of Component Communication

Use an app component to hold data.
Use a bike component to render data bound from the app component using @api.

Next Steps

Learn about deploying code and the component environment in subsequent units.

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Description

This quiz focuses on the creation of Lightning Web Components, covering essential topics such as component file structure and JavaScript methods. You'll learn to implement lifecycle hooks and build custom components like the productCard. Test your knowledge on building and managing components in Salesforce.