Salesforce-JavaScript-Developer Exam Questions With Explanations

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Salesforce Salesforce-JavaScript-Developer Exam Sample Questions 2025

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

22214 already prepared
Salesforce Spring 25 Release18-Sep-2025
221 Questions
4.9/5.0

Given HTML below:
1. Universal Container
2. Applied Shipping
3. Burlington Textiles

Which statement adds the priority = account CSS class to the universal Containers row ?

A. Document .querySelector(‘#row-uc’).classes.push(‘priority-account’);

B. Document .queryElementById(‘row-uc’).addclass(‘priority-account’);

C. Document .querySelector(‘#row-uc’).classList.add(‘priority-account’);

D. Document .querySelectorALL(‘#row-uc’).classList.add(‘priority-account’);

C.   Document .querySelector(‘#row-uc’).classList.add(‘priority-account’);

Explanation:

The document.querySelector('#row-uc') call returns the

element with id="row-uc". Its classList property provides a DOMTokenList of all classes on the element, with an add(...) method to append a new class without disturbing existing ones. Option A is invalid because there’s no .classes property or .push() on DOM elements. Option B mistypes getElementById and uses a non-existent .addclass(). Option D calls querySelectorAll, which returns a NodeList; you’d then need to iterate over each node to add the class.

Refer to the code below: Let inArray =[ [ 1, 2 ] , [ 3, 4, 5 ] ]; Given the code below: const delay = sync delay => { Return new Promise((resolve, reject) => { setTimeout (resolve, delay);});}; const callDelay =async () =>{ const yup =await delay(1000); console.log(1); What is logged to the console?

A. 1 2 3

B. 1 3 2

C. 1 3 2

D. 2 3 1

D.   2 3 1

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);

Given two expressions var1 and var2. What are two valid ways to return the logical AND of the two expressions and ensure it is data type Boolean ?
Choose 2 answers:

A. Boolean(var1 && var2)

B. var1 && var2

C. var1.toBoolean() && var2toBoolean()

D. Boolean(var1) && Boolean(var2)

A.   Boolean(var1 && var2)
D.   Boolean(var1) && Boolean(var2)

Refer to the following code:

Which two statement could be inserted at line 17 to enable the function call on line 18? Choose 2 answers

A. Object.assign (leo, tony);

B. Object.assign (leo. Tiger);

C. leo.roar = () => { console.log('They\'re pretty good!'); );

D. leo.prototype.roar = ( ) =>( console.log('They\'re pretty good!'); };

A.   Object.assign (leo, tony);
C.   leo.roar = () => { console.log('They\'re pretty good!'); );

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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.