SALESFORCE-PD1 User Interface Practice Test 4 — 15 Questions

Question 1

A developer creates a Lightning Web Component that includes a third-party JavaScript library loaded via a Static Resource. In which lifecycle hook should the third-party library be initialized?

Accepted Answer

connectedCallback. The connectedCallback lifecycle hook fires when a component is inserted into the DOM, making it the correct place to initialize third-party libraries that need a DOM element to attach to. At this point, the component's template elements exist and the library can be safely instantiated.

Answer

disconnectedCallback

Answer

renderedCallback

Answer

constructor

Question 2

A developer is working with a Lightning Web Component and needs to access a child component's public method from the parent component. How is this achieved?

Accepted Answer

Invoke the method directly on the child element reference obtained via template.querySelector().. Public methods on child components must be decorated with @api and invoked via this.template.querySelector().methodName().

Answer

Bind the child method to a public @api property on the parent.

Answer

Fire an application event from the parent to the child.

Answer

Use document.getElementById() to find the child element.

Question 3

Which lifecycle hook in a Lightning Web Component is called after every render of the component?

Accepted Answer

renderedCallback. The renderedCallback hook is invoked after every render of the component, including the initial render and subsequent re-renders. It is used for logic that needs to run after the DOM is updated, such as manipulating the DOM or accessing rendered elements.

Answer

constructor

Answer

connectedCallback

Answer

errorCallback

Question 4

A developer needs to navigate to a record detail page from a Lightning Web Component. Which service should be used?

Accepted Answer

lightning/navigation. The lightning/navigation service provides the NavigationMixin, which allows Lightning Web Components to navigate to record detail pages, list views, and other pages using standard navigation. It is the recommended way to navigate within Salesforce.

Answer

lightning/pageReference

Answer

window.location.href

Answer

lightning/uiRecordApi

Question 5

A developer is building a Visualforce page that uses a custom controller and needs to display a message to the user when an error occurs. Which class and method should be used?

Accepted Answer

ApexPages.addMessage(). ApexPages.addMessage() adds an ApexPages.Message to the page messages list.

Answer

ApexPages.currentPage().getParameters().put()

Answer

Database.addError()

Answer

System.debug()

Question 6

A developer is writing a custom wire adapter or working with custom data in LWC and needs to manually provision data or force a refresh of wire data. Which function should be imported from lightning/uiRecordApi or related wire modules?

Accepted Answer

refreshApex. refreshApex is used to imperatively refresh data provisioned by an Apex wire adapter.

Answer

reloadRecord

Answer

updateRecordCache

Answer

getRecordRefresh

Question 7

What is the correct file extension for a Lightning Web Component HTML template file?

Accepted Answer

.html. LWC HTML template files must use the .html extension and share the component base name.

Answer

.vfp

Answer

.page

Answer

.cmp

Question 8

A developer needs to configure a Lightning Web Component to be available for use on Lightning Record Pages. Which configuration entry must be present in the component's metadata file (.js-meta.xml)?

Accepted Answer

lightning__RecordPage. To expose a Lightning Web Component on Lightning Record Pages, the .js-meta.xml file must include the <target> lightning__RecordPage. This target tells the Lightning framework that the component is eligible to be dragged onto record page layouts in Lightning App Builder. Other targets correspond to different surfaces such as app pages, home pages, or utility bars.

Answer

lightning__AppPage

Answer

lightning__GlobalAction

Answer

lightning__UtilityBar

Question 9

A developer wants to conditionally display an HTML element in a Lightning Web Component template based on a boolean property named 'isVisible'. Which directive should be used?

Accepted Answer

lwc:if. lwc:if is the modern conditional directive in LWC.

Answer

renderIf

Answer

aura:if

Answer

v:if

Question 10

A developer needs to catch unhandled JavaScript errors in a Lightning Web Component hierarchy so the entire app doesn't crash. Which lifecycle hook handles errors thrown by descendant components?

Accepted Answer

errorCallback. errorCallback() is invoked when a descendant component throws an error in any of its lifecycle hooks or event handlers.

Answer

catchCallback

Answer

disconnectedCallback

Answer

faultCallback

Question 11

What is the correct syntax to reference a custom label in a Lightning Web Component JavaScript file?

Accepted Answer

import labelName from '@salesforce/label/LabelName';. In Lightning Web Components (LWC), custom labels are imported using the standard ES6 import syntax from the special '@salesforce/label' module. The correct syntax is `import labelName from '@salesforce/label/LabelName';`, where `LabelName` is the API name of the custom label. This import makes the label's value available as a JavaScript variable that can be used in the component's template or logic. This approach is specific to LWC and differs from Aura or Visualforce.

Answer

Label.get('LabelName')

Answer

System.Label.LabelName

Answer

$Label.LabelName

Question 12

A developer is configuring a Lightning Web Component that uses the Lightning Message Service (LMS). Which module must be imported to publish a message on a message channel?

Accepted Answer

lightning/messageService. publish function and the message channel reference are imported from lightning/messageService and the channel definition file respectively.

Answer

lightning/uiRecordApi

Answer

lightning/empApi

Answer

lightning/navigation

Question 13

A developer is creating a Lightning Web Component and needs to iterate over a list of items in the HTML template. Which directive should be used?

Accepted Answer

for:each. LWC templates use the for:each directive to iterate over arrays, with for:item specifying the iteration variable and for:index providing the optional index. Each iterated element must have a unique key attribute (typically the record Id) to help the framework's diffing algorithm efficiently update the DOM.

Answer

repeat:for

Answer

apex:repeat

Answer

aura:iteration

Question 14

A developer is writing a Visualforce page with custom controller logic and needs to ensure that database operations are executed transactionally. What happens by default when an unhandled exception occurs during a controller action method?

Accepted Answer

The entire transaction is rolled back.. In Visualforce with a custom controller, an unhandled exception during a controller action method causes the entire transaction to roll back by default. Salesforce wraps the request in a database transaction, so any DML performed before the exception is undone, preserving atomicity.

Answer

The user is redirected to the login page.

Answer

Only partial records are saved; successful ones are committed.

Answer

Changes are committed and an email is sent to the admin.

Question 15

A developer is implementing a Lightning Web Component that handles drag-and-drop functionality. Which native DOM event is typically intercepted to allow a drop action on an element?

Accepted Answer

dragover and preventDefault(). To allow a drop on an element, the developer must intercept the 'dragover' event and call preventDefault() on it. By default, browsers do not allow dropping on an element; calling preventDefault() in the dragover handler signals that the element is a valid drop target, after which the 'drop' event fires. This is the standard HTML5 drag-and-drop contract.

Answer

dragstart

Answer

dropstart

Answer

mousedown