Salesforce JavaScript Developer Practice Questions: 20 Questions (2026)

Hey friends,

These 20 Salesforce JavaScript Developer practice questions are original questions weighted like the real exam's seven sections, each with the answer and an explanation in a dropdown. I wrote every one from the official exam guide objectives and MDN's JavaScript reference. None are real exam questions.

The real exam has 60 scored questions in 105 minutes, and the passing score is 65%. So aim for 13 of these 20, then read the explanation for every miss, including lucky guesses. Most questions show code and ask what it logs, so run them in your browser console afterward.

Split here: Objects, Functions, and Classes 25% (5 questions), Variables, Types, and Collections 23% (5), Browser and Events 17% (3), Asynchronous Programming 13% (3), Debugging and Error Handling 7% (2), Server Side JavaScript 8% (1), Testing 7% (1). For the topic map, see my JavaScript Developer study guide.

Variables, Types, and Collections (23%): 5 questions

Question 1. What does this code log?

1console.log(typeof null, typeof [], typeof undefined);

• A. null array undefined
• B. object object undefined
• C. object array undefined
• D. null object undefined

Question 2. What does this code log?

1console.log(1 + '2', '3' - 1, true + 1);

• A. 3 2 2
• B. '12' 2 2
• C. 12 2 2
• D. 12 NaN 2

Question 3. Which of these values are falsy? Choose 3.

• A. 0
• B. '0'
• C. ''
• D. []
• E. NaN

Question 4. A developer needs a new array with only the active accounts' names. Which line does that without changing accounts?

1const accounts = [
2  { name: 'Acme', active: true },
3  { name: 'Globex', active: false },
4];

• A. accounts.forEach(a => a.active && a.name)
• B. accounts.filter(a => a.active).map(a => a.name)
• C. accounts.splice(1, 1)
• D. accounts.map(a => a.active ? a.name : null)

Question 5. What does this code log?

1const json = '{"id": 7, "tags": ["a", "b"]}';
2const obj = JSON.parse(json);
3console.log(obj.tags.length, JSON.stringify({ id: obj.id, skip: undefined }));

• A. 2 {"id":7,"skip":undefined}
• B. 2 {"id":7}
• C. 2 {"id":7,"skip":null}
• D. undefined {"id":7}

Objects, Functions, and Classes (25%): 5 questions

Question 6. What does this code log?

1console.log(total);
2var total = 5;
3console.log(count);
4let count = 5;

• A. undefined, then a ReferenceError
• B. 5, then 5
• C. undefined, then undefined
• D. A ReferenceError on line 1

Question 7. What does this code log?

1const counter = {
2  count: 0,
3  incLater() {
4    setTimeout(() => { this.count++; console.log(this.count); }, 0);
5  },
6};
7counter.incLater();

• A. NaN
• B. 1
• C. undefined
• D. A TypeError

Question 8. What does this code log?

1class Animal {
2  speak() { return 'generic'; }
3}
4class Dog extends Animal {
5  speak() { return `woof, not ${super.speak()}`; }
6}
7console.log(new Dog().speak());

• A. generic
• B. woof, not generic
• C. woof, not undefined
• D. A SyntaxError

Question 9. A module file utils.js has export default function format() {} and export const VERSION = '1.0';. Which import gets both?

• A. import { format, VERSION } from './utils.js';
• B. import format, { VERSION } from './utils.js';
• C. import * as format from './utils.js';
• D. const { format, VERSION } = require('./utils.js');

Question 10. What does this code log?

1for (var i = 0; i < 3; i++) {
2  setTimeout(() => console.log(i), 0);
3}

• A. 0 1 2
• B. 3 3 3
• C. 0 0 0
• D. 2 2 2

Browser and Events (17%): 3 questions

Question 11. A list has 500 rows, each needing a click handler. What's the most efficient approach?

• A. Add a listener to every row
• B. Add one listener to the parent list and check event.target
• C. Use inline onclick attributes
• D. Poll for clicks with setInterval

Question 12. A button inside a form should run custom code and must not submit the form or let the click reach parent listeners. Which two calls are needed? Choose 2.

• A. event.preventDefault()
• B. event.stopPropagation()
• C. return true
• D. event.cancelBubble = false

Question 13. A developer wants code to pause in the browser at a specific line, but only when amount is over 1000. What should they use?

• A. console.log(amount)
• B. A conditional breakpoint in the browser dev tools Sources panel
• C. alert(amount)
• D. console.table(amount)

Asynchronous Programming (13%): 3 questions

Question 14. What order does this code log?

1console.log('A');
2setTimeout(() => console.log('B'), 0);
3Promise.resolve().then(() => console.log('C'));
4console.log('D');

• A. A B C D
• B. A D B C
• C. A D C B
• D. A C D B

Question 15. Three independent API calls must all succeed before the page renders, and the page should show an error if any fails. Which is best?

• A. await each call in sequence
• B. Promise.all with all three
• C. Promise.any with all three
• D. Promise.race with all three

Question 16. What does this code log?

1async function getValue() {
2  return 10;
3}
4const v = getValue();
5console.log(v instanceof Promise);

• A. false
• B. true
• C. 10
• D. undefined

Debugging and Error Handling (7%): 2 questions

Question 17. What does this code log?

1try {
2  JSON.parse('{bad json}');
3  console.log('parsed');
4} catch (e) {
5  console.log(e.name);
6} finally {
7  console.log('done');
8}

• A. parsed, done
• B. SyntaxError, done
• C. TypeError, done
• D. done

Question 18. Which console method shows an array of objects as a sortable table in the browser console?

• A. console.dir
• B. console.table
• C. console.group
• D. console.assert

Server Side JavaScript (8%): 1 question

Question 19. A Node.js project needs a package for tests only, not in production. Which command adds it correctly?

• A. npm install jest
• B. npm install --save-dev jest
• C. npm install -g jest
• D. npm init jest

Testing (7%): 1 question

Question 20. This test always passes, even when add is broken. Why?

1test('adds numbers', () => {
2  const result = add(2, 3);
3  expect(result);
4});

• A. The test name is wrong
• B. It has no matcher, so nothing is asserted. Use expect(result).toBe(5)
• C. It needs to be async
• D. add must be mocked

How did you do?

13 or more: you're near the 65% line, so drill your weak sections. Under 13: go back to the topic guides, then retest. The fastest progress comes from rerunning the code you missed and changing one thing at a time.

Here's why I care about practice questions so much. I earned 17 Salesforce certifications, and Focus on Force was a big part of that. My early approach was study guide first, tests later. Flipping it, taking practice tests fast and often, cut my study time way down. Cert Lab is my version of that: fast testing with explanations that link to current docs.

FAQ

How many questions are on the Salesforce JavaScript Developer exam?

60 scored multiple-choice or multiple-select questions, plus up to five unscored ones, in 105 minutes.

What's the passing score?

65%.

How much does the exam cost?

US$200, and a retake is US$100, plus applicable taxes.

Are these real exam questions?

No. I wrote all 20 from the official exam objectives. They test the same skills, not the same questions.

Where should you go next?

• The JavaScript Developer study guide maps every exam section.
• JavaScript promises and closures, the two topics people miss most.
• The event loop for output-order questions.

Nick Frates, a senior Salesforce developer with 17 certifications, built the JavaScript Developer Cert Lab at nickfrates.com: rapid-fire practice questions for every exam section, each answer explained.

Hope this helps!

Best,

Nick