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

A developer has an is Dog function that takes one argument cat. They want to schedule the function to run every minute. What is the correct syntax for scheduling this function?

A. setInterval(isDog, 60000,'cat');

A.   setInterval(isDog, 60000,'cat');

Refer to the following code:





<script>
function displayMessage(ev) {
ev.stopPropagation();
console.log(‘Inner message.’);
}
const elem = document.getElementById(‘myButton’);
elem.addEventListener(‘click’ , displayMessage);
</script>

What will the console show when the button is clicked?

A. Outer message

B. Outer message Inner message

C. Inner message Outer message

D. Inner message

D.   Inner message

Refer to the following object.

How can a developer access the fullName property for dog?

A. Dog.fullName

B. Dog.fullName ( )

C. Dog, get, fullName

D. Dog, function, fullName

A.   Dog.fullName

Refer to code below:
Function muFunction(reassign){
Let x = 1;
var y = 1;
if( reassign ) {
Let x= 2;
Var y = 2;
console.log(x);
console.log(y);}
console.log(x);
console.log(y);}
What is displayed when myFunction(true) is called?

A. 2 2 1 1

B. 2 2 undefined undefined

C. 2 2 1 2

D. 2 2 2 2

C.   2 2 1 2

Explanation:

This question tests your understanding of variable scoping in JavaScript, specifically the difference between let and var.
Inside the if Block (reassign is true):
let x = 2; creates a new, block-scoped variable x. This variable is separate from the x declared outside the if block. When console.log(x); is called, it accesses this new block-scoped x, which has a value of 2.
var y = 2; re-declares the variable y. Because var is function-scoped, this declaration simply overwrites the value of the y declared outside the if block. When console.log(y); is called inside the if block, it logs the new value, which is 2.

So, the first two console.log statements display 2 and 2.

Outside the if Block:
The first console.log(x); is outside the if block. It references the original x declared with let at the beginning of the function. This variable was not affected by the let x = 2 declaration inside the if block. Therefore, it logs the original value, which is 1.
The second console.log(y); is also outside the if block. Since the var y = 2 declaration inside the if block affected the function-scoped y, this y now holds the value 2. Therefore, it logs 2.

Combining these results, the output is 2 2 1 2.

Refer to code below:
function Person() {
this.firstName = ’John’;
}
Person.prototype ={
Job: x => ‘Developer’
};
const myFather = new Person();
const result =myFather.firstName + ‘ ‘ + myFather.job();
What is the value of the result after line 10 executes?

A. Error: myFather.job is not a function

B. Undefined Developer

C. John undefined

D. John Developer

D.   John Developer

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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.