Salesforce-JavaScript-Developer Exam Questions With Explanations

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Salesforce Salesforce-JavaScript-Developer Exam Sample Questions 2026

Start practicing today and take the fast track to becoming Salesforce Salesforce-JavaScript-Developer certified.

22714 already prepared
Salesforce 2026 Release
271 Questions
4.9/5.0

Refer to the code below:

What is the result when the Promise in the execute function is rejected?

A. Resolved1 Resolved2 Resolved3 Resolved4

B. Rejected

C. Rejected Resolved

D. Rejected1 Rejected2 Rejected3 Rejected Rejected Rejected4

C.   Rejected Resolved

A developer creates a class that represents a blog post based on the requirement that a
Post should have a body author and view count.
The Code shown Below:
Class Post {
// Insert code here
This.body =body
This.author = author;
this.viewCount = viewCount;
}
}
Which statement should be inserted in the placeholder on line 02 to allow for a variable to be set to a new instanceof a Post with the three attributes correctly populated?

A. super (body, author, viewCount) {

B. Function Post (body, author, viewCount) {

C. constructor (body, author, viewCount) {

D. constructor() {

C.   constructor (body, author, viewCount) {

Refer to following code:
class Vehicle {
constructor(plate) {
This.plate =plate;
}
}
Class Truck extends Vehicle {
constructor(plate, weight) {
//Missing code This.weight = weight;
}
displayWeight() {
console.log(‘The truck ${this.plate} has a weight of ${this.weight} lb.’);}}
Let myTruck = new Truck(‘123AB’, 5000);
myTruck.displayWeight();
Which statement should be added to line 09 for the code to display ‘The truck 123AB has a weight of 5000lb.’?

A. Super.plate =plate;

B. super(plate);

C. This.plate =plate;

D. Vehicle.plate = plate;

B.   super(plate);

Refer to the string below:
const str = 'Salesforce';
Which two statements result in the word 'Sales'?
Choose 2 answers

A. str.substr(1, 5);

B. str.substr (0, 5);

C. str.substring (1, 5);

D. str.substring (0, 5);

B.   str.substr (0, 5);
D.   str.substring (0, 5);

A developer at Universal Containers is creating their new landing page based on HTML, CSS, and JavaScript. The website includes multiple external resources that are loaded when the page is opened. To ensure that visitors have a good experience, a script named personalizeWebsiteContent needs to be executed when the webpage Is loaded and there Is no need to wait for the resources to be available.
Which statement should be used to call personalizeWebsiteContent based on the above business requirement?

A. windows,addEventListener('load', personalizeWebsiteContent);

B. windows,addEventListener('DOMContent Loaded ', personalizeWebsiteContent);

C. windows,addEventListener('onload', personalizeWebsiteContent);

D. windows,addEventListener('onDOMCContentLoaded', personalizeWebsiteContent);

A.   windows,addEventListener('load', personalizeWebsiteContent);

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Salesforce JavaScript Developer I – Frequently Asked Questions

The certification validates modern JavaScript (ES6+) skills in the Salesforce ecosystem—especially with Lightning Web Components (LWC), testing, and security. It tells employers you can write maintainable, performant, and secure front-end code on the Salesforce Platform.
Typically ~60 questions (multiple-choice/multiple-select), about 100–110 minutes, and a passing score around the mid-60% range. Always confirm current numbers before you register.
You can test via online proctoring or at a Pearson VUE test center, depending on availability in your region.
The blueprint typically includes:
  • Core JavaScript: variables, functions, scope, objects, arrays
  • Asynchronous patterns: promises, async/await
  • Browser & events: propagation, default behavior
  • Error handling & debugging
  • Testing with Jest
  • LWC fundamentals: decorators, events, data access
Prioritize let/const, arrow functions, template literals, destructuring, rest/spread, modules (import/export), classes, Map/Set, promises, async/await, and array methods (map/filter/reduce).
Expect code that evaluates promise chains, microtask timing, and try/catch with async/await. You should handle rejections cleanly and avoid callback hell.
You’ll analyze outputs, fix scope/hoisting bugs, refactor to ES6+, and identify anti-patterns. Expect snippets involving events and import/export usage. Try realistic code challenges.
The emphasis is front-end JS for LWC. Know npm basics, project structure, linting, and Jest—deep Node internals are not the focus.
Understand capture/bubble, preventing defaults, custom events, and how LWC leverages standard browser patterns. Know timers, fetch, and common Web APIs.
The session typically pauses and lets you reconnect; repeated issues can end the attempt. Use a wired connection, close heavy apps, and run pre-checks.
Take timed full-length mocks, then review every explanation. Convert mistakes into flashcards and retest weak topics with targeted quizzes.
Typically you can retake after a short wait (e.g., 1 day) for the first retake and ~14 days thereafter, with a cap per release cycle. Always confirm the current policy.
Combine Trailhead, MDN, and hands-on LWC projects. Reinforce with exam-focused notes, flashcards, and mocks from salesforceking.com.
Learn @api, @wire, component composition, and data access. Practice Jest unit tests: DOM queries, events, and mocking wire adapters.
Use @salesforce/sfdx-lwc-jest, mock Apex and wire adapters, flush promises for async, and assert both DOM changes and events.
Understand try/catch for sync/async, promise rejections, and common errors (TypeError, ReferenceError). Practice with real snippets and devtools.
@wire is declarative/reactive and can leverage caching; imperative calls give you programmatic control (e.g., conditional execution). Know loading/error states and best practices for each.
High-frequency areas: array methods, prototypes/classes, closures, equality (== vs ===), truthy/falsy, and modules.
Know Lightning Web Security/Locker basics, safe DOM patterns, and XSS prevention; for performance, avoid unnecessary re-renders, cache intelligently, and manage state cleanly.
Add it to LinkedIn and your resume, publish an LWC demo repo, write a short blog post on a tricky topic you mastered, and reference client/stakeholder impact where possible.