SALESFORCE-PD1 User Interface Practice Test 5 — 15 Questions

Question 1

A developer has a Lightning Web Component with a reactive property 'recordId'. How should the property be decorated to ensure it receives the current record ID when placed on a record page?

Accepted Answer

@api recordId;. The @api decorator makes a property public and reactive, allowing a parent component or the Lightning record page to pass the recordId into the component. On a record page, the framework automatically injects the current record ID into any public property named recordId. Without @api, the property is private and will not receive the value.

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@wire recordId;

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@track recordId;

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@wire(getRecord) recordId;

Question 2

A developer needs to access a specific HTML element in a Lightning Web Component template imperatively. Which method should be called?

Accepted Answer

this.template.querySelector(). In Lightning Web Components, to access an element in the template imperatively, you must use this.template.querySelector() with a CSS selector. This method scopes the query to the component's template, ensuring encapsulation and preventing access to elements outside the component. It returns the first matching element.

Answer

window.findElement()

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this.findElement()

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document.querySelector()

Question 3

Which tag is used in Visualforce to include custom CSS stylesheets?

Accepted Answer

. is used to include external CSS files in Visualforce.

Answer

Answer

<apex:css>

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<apex:style>

Question 4

A developer is writing an Aura component and needs to dynamically create a component at runtime. Which JavaScript method should be used?

Accepted Answer

$A.createComponent(). $A.createComponent() is the Aura framework's factory method for dynamically instantiating a component at runtime by name, returning a callback with the new component instance that can then be inserted into the DOM via component.set('v.body', ...). It is the only supported way to create Aura components programmatically rather than declaratively in markup.

Answer

document.createElement()

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Aura.create()

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component.new()

Question 5

A developer is building a Lightning Web Component and needs to perform validation on an input field before submission. Which method on a lighting-input element checks validity?

Accepted Answer

checkValidity(). lightning-input exposes a checkValidity() method that returns true if the input satisfies all its constraints (required, minlength, pattern, type-specific validation) and false otherwise, while also firing an invalid event and setting the validity property. It mirrors the native HTMLInputElement.checkValidity() API, which the base component wraps.

Answer

verify()

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isValid()

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validate()

Question 6

Which base component should be used in LWC to display a tabular grid of data with sorting and row selection?

Accepted Answer

lightning-datatable. lightning-datatable is the correct base component for displaying tabular data with built-in support for sorting, row selection, and other features like inline editing. It is designed specifically for LWC and provides a rich set of attributes and events to handle data grid functionality.

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lightning-grid

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lightning-table

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apex:pageBlockTable

Question 7

A developer is building a Lightning Web Component and needs to listen to a custom event dispatched by a child component. How is the event listener attached in the parent HTML template?

Accepted Answer

onmyevent={handler}. Child events are listened to using on<eventname> attribute syntax in the parent template.

Answer

event-myevent={handler}

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on-myevent={handler}

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listener={handler}

Question 8

A developer needs to format a currency value according to the user's locale in a Lightning Web Component HTML template. Which base component should be used?

Accepted Answer

lightning-formatted-number. lightning-formatted-number is the correct base component because it formats numeric values, including currency, according to the user's locale. It supports a 'format-style' attribute set to 'currency' and automatically applies the correct currency symbol, decimal separator, and grouping based on the user's locale settings. This is the standard LWC component for locale-aware number formatting.

Answer

lightning-input

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apex:outputText

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ui:outputCurrency

Question 9

A developer is working with a Lightning Web Component and needs to ensure reactive updates occur when an object property or array element changes inside a tracked property. What is the correct approach in modern LWC?

Accepted Answer

Reassign the property reference (e.g., this.myObj = {...this.myObj}).. Assigning a new object or array reference (mutation via replacement) triggers reactivity in LWC tracked properties.

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Use @track on every inner property.

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Call component.forceUpdate().

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Mutate the nested property directly; LWC automatically deep-tracks all mutations.

Question 10

Which tag is used in Visualforce to output field labels and values dynamically based on sObject field definitions?

Accepted Answer

. renders field values with correct formatting and related labels.

Answer

<apex:field>

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<apex:inputField>

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<apex:outputText>

Question 11

A developer creates a Lightning Web Component that consumes data from a wire adapter. The wire adapter returns an object with 'data' and 'error' properties. What is this pattern called in LWC?

Accepted Answer

Wired property / result object pattern. Wire adapters return a wrapper object containing data and error properties.

Answer

Event emitter pattern

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Promise chaining

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Async/await callback pattern

Question 12

A developer is building a Lightning Web Component and needs to navigate to a URL that is external to Salesforce. Which PageReference type should be used with NavigationMixin?

Accepted Answer

standard__webPage. standard__webPage is the PageReference type for navigating to external URLs or web pages.

Answer

standard__recordPage

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standard__namedPage

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standard__objectPage

Question 13

A developer is building a Lightning Web Component and needs to dispatch a custom event. Which constructor should be used to create the event?

Accepted Answer

CustomEvent. In Lightning Web Components, custom events are created using the CustomEvent constructor. The syntax is `new CustomEvent('eventName', { detail: {...} })`. This is the standard DOM API for creating custom events, and LWC uses it to dispatch events from child to parent components.

Answer

Event

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AuraEvent

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LightningEvent

Question 14

Which TWO lifecycle hooks are available in Lightning Web Components? Choose 2 answers.

Accepted Answer

renderedCallback. Option A, renderedCallback, is correct because it is a genuine Lightning Web Components lifecycle hook that fires after every render of a component, allowing you to perform logic that depends on the DOM being updated. Option C, connectedCallback, is also correct because it is a standard LWC lifecycle hook invoked when the component is inserted into the DOM, commonly used for initialization such as wiring up data or adding event listeners. The other options do not belong: init, componentDidMount, and willMount are lifecycle hooks from other frameworks or Aura/Lightning Aura terminology, not valid LWC lifecycle hooks.

Answer

init

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componentDidMount

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willMount

Question 15

A developer is using the Lightning Message Service and needs to unsubscribe from a message channel when a component is destroyed. In which lifecycle hook should unsubscribe be called?

Accepted Answer

disconnectedCallback. The disconnectedCallback lifecycle hook fires when a component is removed from the DOM, making it the correct place to unsubscribe from a Lightning Message Channel. Failing to unsubscribe here causes memory leaks and errors when messages arrive for a destroyed component.

Answer

connectedCallback

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constructor

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renderedCallback