Salesforce Certified B2B Commerce Administrator Practice Test - Questions Answers, Page 21

The lightning-record-edit-form component allows a developer to view or edit a record while maintaining control over specifying its layout and set of fields. It is a wrapper component that accepts a record ID and an object API name, and displays fields with their labels and current values. The developer can use lightning-input-field components inside the lightning-record-edit-form to create editable fields, and lightning-output-field components or other display components to show read-only information. The lightning-record-edit-form component also implements Lightning Data Service, which means it does not require additional Apex controllers to create or update records, and it handles field-level security and sharing automatically.

The Lightning Message Service (LMS) is a feature that allows communication across different UI technologies, such as Lightning Web Components, Aura Components, and Visualforce pages. LMS uses message channels to publish and subscribe to messages.A message channel is a custom metadata type that defines the shape and scope of the messages1.The lightning_commerce_cartChanged channel is a standard message channel that is used by the B2B Commerce Cloud platform to notify components of changes to the cart items and quantities2. A developer can use the LMS API to subscribe to events on this channel and update the custom component accordingly.The developer needs to import the lightning/messageService module and the lightning_commerce_cartChanged channel in the JavaScript file of the custom component, and then use the subscribe method to register a callback function that handles the message payload3. For example:

// cartCustomComponent.js import { LightningElement, wire } from 'lwc'; import { subscribe, MessageContext } from 'lightning/messageService'; import CART_CHANGED_CHANNEL from '@salesforce/messageChannel/lightning_commerce_cartChanged__c';

export default class CartCustomComponent extends LightningElement { // Declare a message context @wire(MessageContext) messageContext;

// Declare a subscription variable subscription = null;

// Subscribe to the message channel in the connected callback connectedCallback() { this.subscribeToMessageChannel(); }

// Subscribe to the message channel using the LMS API subscribeToMessageChannel() { if (!this.subscription) { this.subscription = subscribe( this.messageContext, CART_CHANGED_CHANNEL, (message) => this.handleCartChange(message) ); } }

// Handle the message payload and update the component logic handleCartChange(message) { // Do something with the message payload, such as: // - Display the cart items and quantities // - Calculate the cart total // - Apply discounts or taxes // - etc. } }

The Lightning Message Service (LMS) allows communication across different UI technologies on a Lightning page, such as Lightning Web Components, Aura Components, and Visualforce pages. LMS uses message channels to publish and subscribe to messages.A message channel is a custom metadata type that defines the shape and scope of the messages1. The scope of a message channel determines which components can receive signaling from it.There are two possible scopes: application and component1.The application scope means that any component on the page can receive signaling from the message channel, regardless of its position in the DOM hierarchy1.The component scope means that only components that share a common ancestor can receive signaling from the message channel1. Therefore, the correct answer is B. page (anywhere on it), because it corresponds to the application scope of a message channel.Reference:Use Lightning Message Service

To handle the subscription lifecycle of a Message Channel, a developer should implement two methods in a Lightning web component: subscribe() and unsubscribe(). The subscribe() method is used to register a callback function that handles the messages published on the message channel. The unsubscribe() method is used to remove the subscription and stop receiving messages.Both methods are part of the Lightning Message Service API, which is imported from the lightning/messageService module1. For example:

// Import the Lightning Message Service API import { subscribe, unsubscribe, MessageContext } from 'lwc/messageService';

// Declare a message context @wire(MessageContext) messageContext;

// Declare a subscription variable subscription = null;

// Subscribe to the message channel in the connected callback connectedCallback() { this.subscribeToMessageChannel(); }

// Subscribe to the message channel using the LMS API subscribeToMessageChannel() { if (!this.subscription) { this.subscription = subscribe( this.messageContext, MESSAGE_CHANNEL, // The name of the message channel (message) => this.handleMessage(message) // The callback function ); } }

// Unsubscribe from the message channel in the disconnected callback disconnectedCallback() { this.unsubscribeFromMessageChannel(); }

// Unsubscribe from the message channel using the LMS API unsubscribeFromMessageChannel() { unsubscribe(this.subscription); this.subscription = null; }

Using a single underscore because this is allowed when it comes to naming a Lightning web component's folder and associated files.However, it is not recommended because it does not map to kebab case in markup, which is the convention for web components2. The other options are incorrect because they violate the naming rules for Lightning web components.The folder and its files must follow these naming rules3:

Must begin with a lowercase letter

Must contain only alphanumeric or underscore characters

Must be unique in the namespace

Can't include whitespace

Can't end with an underscore

Can't contain two consecutive underscores

Can't contain a hyphen (dash)

<target>lightningCommunity_Page</target> because this is the element that should be included in the component's configuration XML file to make the custom component available for the Product Detail page in the store.The target element specifies where the component can be used, and the lightningCommunity_Page value indicates that the component can be used on any Experience Builder page1. The other options are incorrect because they either use invalid or irrelevant elements or values.For example, the builder element is not a valid element for Lightning web components2, the RecordPage value is not a valid target for Lightning web components3, and the isAvailable and isExposed elements are not required for Lightning web components4.Reference:Target a Page Type,Component Configuration File,Target Config File,Expose a Component to Experience Builder

<slot></slot> because this is the element that can be used to pass HTML from a parent component to a child component.The slot element is a placeholder for content that is defined in the parent component and inserted into the child component5.It allows creating reusable components with dynamic content6. For example, suppose there is a parent component that defines some HTML content inside a child component:

<!-- parent.html --> <template> <c-child>

This is some HTML content passed from the parent to the child. </c-child> </template>

The child component can use the slot element to render the content from the parent:

<!-- child.html --> <template> <h1>This is the child component.</h1> <slot></slot> <!-- This will display the content from the parent --> </template>

The output will look like this:

This is the child component. This is some HTML content passed from the parent to the child.

The correct way to demonstrate the passing of a message from the grandchild component to the grandparent component is by using an attribute on the child component to pass the message. This can be done by using the @api decorator in the grandchild component and then handling the message in the grandparent component with the handlemessage method. For example:

<!-- grandchild.html --> <template> <lightning-button label=''Send Message'' onclick={handleClick}></lightning-button> </template>

// grandchild.js import { LightningElement, api } from 'lwc';

export default class Grandchild extends LightningElement { // Declare an attribute to pass the message @api message = 'Hello from grandchild';

// Handle the button click and fire an event handleClick() { // Create a custom event with the message as detail const event = new CustomEvent('message', { detail: this.message }); // Dispatch the event from this component this.dispatchEvent(event); } }

<!-- child.html --> <template> <c-grandchild onmessage={handleMessage}></c-grandchild> </template>

// child.js import { LightningElement } from 'lwc';

export default class Child extends LightningElement { // Handle the message event from the grandchild component handleMessage(event) { // Get the message from the event detail const message = event.detail; // Fire another event with the same message to pass it to the parent component this.dispatchEvent(new CustomEvent('message', { detail: message })); } }

<!-- parent.html --> <template> <c-child onmessage={handleMessage}></c-child> </template>

// parent.js import { LightningElement } from 'lwc';

export default class Parent extends LightningElement { // Declare a property to store the message message;

// Handle the message event from the child component handleMessage(event) { // Get the message from the event detail and assign it to the property this.message = event.detail; // Do something with the message, such as display it on the screen console.log(this.message); } }

The Shadow DOM is a standard that provides encapsulation for the internal document object model (DOM) structure of a web component. The DOM is the representation of the HTML elements and attributes of a web page in a tree-like structure. The Shadow DOM allows creating a separate DOM tree for each web component, which is hidden from the main DOM tree.This means that the markup, style, and behavior of the web component are isolated from the rest of the page1. The purposes of the Shadow DOM in a Lightning web component are:

It encapsulates the internal document object model (DOM) structure of a web component. This means that the web component has its own scope and namespace, and does not interfere with other elements on the page.For example, the web component can use its own CSS selectors and variables without affecting or being affected by the global CSS2.The web component can also use custom HTML tags without conflicting with existing or future HTML standards3.

It allows components to be shared while protecting them from being manipulated by arbitrary code. This means that the web component can be reused in different contexts and applications, without worrying about external code changing its functionality or appearance.For example, the web component can be embedded in another web page or application, and it will still work as intended, regardless of the surrounding code4.The web component can also prevent malicious code from accessing or modifying its internal state or data5.