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 Release
221 Questions
4.9/5.0

Considering type coercion, what does the following expression evaluate to? True + ‘13’ + NaN

A. ‘ 113Nan ’

B. 14

C.

‘ true13 ’

14

D. ‘ true13NaN ’

D.   ‘ true13NaN ’

Refer to code below:
Const objBook = {
Title: ‘Javascript’,
};
Object.preventExtensions(objBook);
Const newObjBook = objBook;
newObjectBook.author = ‘Robert’;
What are the values of objBook and newObjBook respectively ?

A. [title: “javaScript”] [title: “javaScript”]

B. {author: “Robert”, title: “javaScript}
Undefined

C. {author: “Robert”, title: “javaScript}
{author: “Robert”, title: “javaScript}

D. {author: “Robert”}
{author: “Robert”, title: “javaScript}

A.   [title: “javaScript”] [title: “javaScript”]

A developer wants to set up a secure web server with Node.js. The developer creates a directory locally called app-server, and the first file is app-server/index.js Without using any third-party libraries, what should the developer add to index.js to create the secure web server?

A. const https =require(‘https’);

B. const server =require(‘secure-server’);

C. const tls = require(‘tls’);

D. const http =require(‘http’);

A.   const https =require(‘https’);

Explanation:

🔎 Key facts:
Node.js has a built-in https module for creating secure (SSL/TLS) web servers.
The http module is for plain, non-secure servers.
The tls module handles lower-level TLS/SSL sockets, but it’s not used directly to serve HTTPS web traffic.
There is no built-in secure-server module — that’s a fake distractor.

Check options:
A. const https = require('https'); ✅
Correct! This loads Node’s core https module, used to create secure HTTPS servers.
B. const server = require('secure-server'); ❌
Not a real Node.js core module.
C. const tls = require('tls'); ❌
This provides raw TLS socket support. Too low-level for setting up a web server.
D. const http = require('http'); ❌
This creates insecure HTTP servers, not HTTPS.
Correct Answer: A. const https = require('https');

📚 Reference:
Node.js Docs – https module
Node.js Docs – http module

let timerId = setTimeout (timedFunction, 1000);
Which statement allows a developer to cancel the scheduled timed function?

A. removeTimeout(timedFunction);

B. removeTimeout(timerId);

C. clearTimeout(timerId);

D. clearTimeout(timedFunction);

C.   clearTimeout(timerId);

Refer to the expression below:
Let x = (‘1’ + 2) == (6 * 2);
How should this expression be modified to ensure that evaluates to false?

A. Let x = (‘1’ + ‘ 2’) == ( 6 * 2);

B. Let x = (‘1’ + 2) == ( 6 * 2);

C. Let x = (1 + 2) == ( ‘6’ / 2);

D. Let x = (1 + 2 ) == ( 6 / 2);

A.   Let x = (‘1’ + ‘ 2’) == ( 6 * 2);

Explanation:

🔍 Original Expression:
let x = ('1' + 2) == (6 * 2);
Breakdown:
'1' + 2 → '12' (string concatenation)
6 * 2 → 12 (number)
'12' == 12 → true (because == does type coercion)

Goal:
We want to modify the expression so it evaluates to false.

Correct Answer:
A. let x = ('1' + ' 2') == (6 * 2);

Why?
'1' + ' 2' → '1 2' (note the space!)
6 * 2 → 12
'1 2' == 12 → false Because '1 2' is not coercible to the number 12.

Why the other options fail:
B. '1' + 2 == 12
✅ true Same as original — still evaluates to true.
C. (1 + 2) == ('6' / 2)
✅ true 3 == 3 — both sides are numbers.
D. (1 + 2) == (6 / 2)
✅ true 3 == 3 again — still true.

🧠 Key Concepts:
+ with a string → triggers string concatenation
== → performs type coercion
To force false, you need non-equivalent values after coercion

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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.