Salesforce Certified JavaScript Developer I Dumps & Exam Questions

Ace the Salesforce Certified JavaScript Developer I exam with our updated 2026 dumps, sample questions, and practical test sets. These materials are aligned with the latest exam blueprint and cover essential JavaScript concepts like ES6+, asynchronous programming, browser APIs, event handling, as well as Salesforce-specific topics like Lightning Web Components (LWC). Whether you're a frontend dev or aiming to become a certified JavaScript developer in the Salesforce ecosystem, our Salesforce Certified JavaScript Developer I dumps help sharpen your skills, improve accuracy, and ensure you're well-prepared to clear the exam on the first try.

Salesforce Certified JavaScript Developer I Dumps & Sample Questions List :

1. What is the output? `console.log(typeof NaN);`

1. `"undefined"`

2. `"number"`

3. `"NaN"`

4. `"string"`

2. Which of the following is a fundamental characteristic of a function declared with the `async` keyword?

1. It always returns a Promise.

2. It can only be called by another `async` function.

3. It blocks the main JavaScript thread until it completes.

4. It can use the `await` keyword, but only if it's inside a `try...catch` block.

3. To debug a Node.js application named `server.js` using the built-in command-line debugger, which command should a developer run?

1. `node server.js`

2. `node inspect server.js`

3. `node --inspect-brk server.js`

4. `node server.js --debug`

4. What does `console.log(Boolean(''))` output?

1. `true`

2. `TypeError`

3. `false`

4. `undefined`

5. A developer adds a testing library to `devDependencies` in `package.json`. When another developer on the team runs `yarn install`, the library is not installed. What is the most likely reason?

1. The yarn cache is corrupt and needs to be cleared with `yarn cache clean`.

2. The `yarn.lock` file was not committed to the repository.

3. The `NODE_ENV` environment variable is set to `production` on the other developer's machine.

4. The developer missed the `--save` flag.

6. Which tool bundles JavaScript modules?

1. ESLint

2. Jest

3. Babel

4. Webpack

7. What is the primary role of the `await` keyword in an `async` function?

1. It can only be used with the `fetch()` API.

2. It blocks the entire JavaScript program until a task is complete.

3. It pauses the execution of the `async` function until a Promise is settled.

4. It converts a regular value into a Promise.

8. Given the function: `const sayHello = () => console.log('Hi!');`. Which code snippet will execute this function exactly once, after a delay of 2 seconds?

1. `setTimeout(sayHello(), 2000);`

2. `setTimeout(sayHello, 2000);`

3. `setInterval(sayHello, 2000);`

4. `delay(sayHello, 2000);`

9. A quality assurance test for a "Buy Now" button passes. Later, a developer removes a CSS class that the test uses to identify the button, causing the test to fail, even though the button is still visible and functional for a user. What type of test result does this failure represent?

1. False Positive

2. True Positive

3. True Negative

4. False Negative

10. What is the output of `['a', 'b'].map(item => item.toUpperCase())`?

1. `[65, 66]`

2. `['A','b']`

3. `['A', 'B']`

4. `['a', 'b']`

11. What does `setTimeout(() => {}, 0)` accomplish?

1. Execution after render cycle

2. Higher priority than promises

3. Immediate execution

4. Guaranteed execution before I/O

12. Which Node.js method reads environment variables?

1. `process.getEnv()`

2. `fs.readEnvSync()`

3. `env.get()`

4. `process.env.VAR_NAME`

13. A developer wants to catch a potential error from an asynchronous operation inside a `setTimeout`. Which `try...catch` implementation is correct for this purpose?

1. `setTimeout(function() { try { countSheep(); } catch (e) { handleError(e); } }, 1000);`

2. `setTimeout(countSheep).catch(e => handleError(e))`

3. `new Promise(() => countSheep()).catch(e => handleError(e))`

4. `try { setTimeout(function() { countSheep(); }, 1000); } catch (e) { handleError(e); }`

14. Which React hook replaces `componentDidMount` for data fetching?

1. `useState`

2. `useEffect`

3. `useCallback`

4. `useMemo`

15. An `async` function `runParallel()` is defined, which returns a promise. Which statement shows the standard 'Promise chaining' syntax to execute the function and handle its successful result?

1. `runParallel().then(function(data){ ... });`

2. `runParallel().done(function(data){ ... });`

3. `runParallel().then(data);`

4. `async runParallel().then(data);`

16. What executes first: `Promise.resolve()` or `setTimeout(fn, 0)`?

1. Random order

2. Synchronous code

3. `setTimeout`

4. `Promise.resolve()`

17. What is logged? `let a = [1,2]; let b = [1,2]; console.log(a == b);`

1. `true`

2. `[1,2] == [1,2]`

3. `false`

4. `TypeError`

18. Which CSS-in-JS library uses tagged template literals?

1. JSS

2. Emotion

3. Tailwind CSS

4. styled-components

19. Given the code: `const pi = 3.1415926;` What is the data type of the variable `pi`?

1. Float

2. Integer

3. Number

4. Double

20. Which method safely accesses `document` in Next.js?

1. `useDocument()`

2. `global.document`

3. `next/document` component

4. `typeof window !== 'undefined'`

21. When debugging JavaScript in a browser's developer tools and paused at a breakpoint, which two of the following are fundamental panels for inspecting the program's state? (Choose 2)

1. Performance Panel

2. Call Stack Panel

3. Sources Panel

4. Scope Panel

22. A developer wants an event listener on a button to fire only the very first time it is clicked. Which two of the following approaches will achieve this? (Choose 2)

1. Inside the handler, explicitly remove the listener using `button.removeEventListener('click', myHandler);`.

2. `button.addEventListener('click', myHandler, { once: true });`

3. Inside the handler, call `event.stopPropagation();`.

4. Inside the handler, check a global flag like `if (hasFired) return;` and then set `hasFired = true;`.

23. What is the primary purpose of the `useState` hook in React?

1. To access context values

2. To manage side effects like data fetching

3. To optimize performance with memoization

4. To store and update component state

24. What is the output of `console.log(typeof null);` in JavaScript?

1. `"null"`

2. `primitive"`"

3. `undefined"`"

4. `object"`"

25. A developer writes `console.log('Page loaded!');` inside a function that runs on page load. Where will this message appear?

1. On the webpage itself, visible to the user.

2. On the browser's JavaScript console

3. In a new `alert()` pop-up window

4. On the terminal console running the web server

26. Given a nested array `let inArray = [[1, 2], [3, 4], [5]];`, which two statements will produce a new, flattened array `[1, 2, 3, 4, 5]`? (Choose 2)

1. `[].concat.apply([], inArray);`

2. `[].concat(...inArray);`

3. `inArray.flat();`

4. `inArray.concat();`

27. Which option is true about JavaScript modules (files imported via `import`) regarding strict mode?

1. Strict mode is disabled by default, but can be enabled with a `'use strict';` directive.

2. Strict mode only applies if the module is imported using a dynamic `import()`.

3. Strict mode is enabled by default, but can be disabled with a `'use no-strict';` directive.

4. JavaScript modules are always in strict mode, with no way to opt out.

28. A developer is creating an image previewer. The user selects a file using an `<input type='file'>`. Which code correctly reads the selected file and prepares it to be used as the `src` for an `<img>` tag?

1. `const reader = new File(); if (file) { reader.readAsDataURL(file); }`

2. `const reader = new FileReader(); if (file) { reader.readAsText(file); }`

3. `const reader = new FileReader(); if (file) { URL.createObjectURL(file); }`

4. `const reader = new FileReader(); if (file) { reader.readAsDataURL(file); }`

29. A developer needs to debug a Node.js web server with a runtime error at an endpoint. They want to test locally and debug using only the terminal. The server starts with server.js. Which command opens the CLI debugger?

1. node -i server.js

2. node inspect server.js

3. node server.js --inspect

4. node start inspect server.js

30. Which two statements are true about the finally block in a try...catch...finally statement? (Choose 2)

1. It only executes if an error is caught in the catch block.

2. Code within a finally block will always execute, even if a return statement exists in the try or catch block.

3. It executes after the try block, but only if no error was thrown.

4. It receives the error object as its first argument.

5. It will execute regardless of whether an error was thrown or caught.

31. What is the primary goal of a "smoke test" suite?

1. To run a small, quick suite of tests that verify the most critical functionalities of the system are working.

2. To test the visual appearance of the user interface against approved designs.

3. To verify the functionality of every single feature in the application.

4. To measure the performance and load capacity of the application.

32. What are two unique features of arrow functions compared to regular functions? Choose 2 answers

1. Arrow functions generate their own 'this' for scope separation.

2. Arrow functions receive a 'parentThis' argument.

3. Arrow functions don't have their own 'this' - they inherit it from enclosing scope.

4. If arrow functions have a single expression, it's automatically returned without 'return' keyword.

33. Refer to the code below: const pi = 3.1415926; What is the data type of pi?

1. Float

2. Double

3. Number

4. Decimal

34. 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?

1. const server = require('secure-server');

2. const https = require('https');

3. const http = require('http');

4. const tls = require('tls');

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

1. str.substr(1, 5);

2. str.substring(0, 5);

3. str.substring(1, 5);

4. str.slice(0, 5);

36. In a Node.js application, what is the purpose of the process.env object?

1. To contain all the command-line arguments passed to the Node.js script.

2. To expose the system's environment variables as a JavaScript object.

3. To manage and interact with child processes spawned by the application.

4. To provide information about the current Node.js process, like its ID and memory usage.

37. Which JavaScript statement changes the text 'In Progress' to 'Completed'?"

1. document.getElementById(\"status\").innerText = 'Completed';

2. document.getElementById(\"status\").innerTEXT = 'Completed';

3. document.getElementById(\"status\").innerHTML = 'Completed';

4. document.getElementById(\"status\").value = 'Completed';

38. Given the following code: let x = ('15' + 10) * 2; What is the value of x?

1. 1520

2. 50

3. 3020

4. 35

39. A developer wants to use a try...catch statement to catch any error that countSheep() may throw and pass it to handleError() function within a setTimeout callback. What is the correct implementation?

1. try { setTimeout(function() { countSheep(); }, 1000); } catch (e) { handleError(e); }

2. setTimeout(() => { countSheep(); }, 1000).catch(e => handleError(e));

3. setTimeout(function() { try { countSheep(); } catch (e) { handleError(e); } }, 1000);

4. try { countSheep(); } catch (e) { handleError(e); } finally { setTimeout(() => {}, 1000); }

40. Given the code below: const copy = JSON.stringify([new String('false'), new Boolean(false), undefined]); What is the value of copy?

1. '[false, {}]'

2. '["false", false, null]'

3. '["false", {}]'

4. '["false", false, undefined]'

41. Which three actions can be done using the JavaScript browser console?

1. View and change security cookies.

2. View, change, and debug the JavaScript code of the page.

3. Run code that is not related to the page.

4. View and change the DOM of the page.

5. Display a report showing the performance of a page.

42. Which statement accurately describes an aspect of promises?

1. .then() manipulates and returns the original promise.

2. In a .then() function, returning results is not necessary since callbacks will catch the result of a previous promise.

3. Arguments for the callback function passed to .then() are optional.

4. .then() cannot be added after a catch.

43. Given a value, which three options can a developer use to detect if the value is NaN?

1. value !== value

2. Number.isNaN(value)

3. value === NaN

4. Object.is(value, NaN)

5. value == Number.NaN

44. A developer wants to leverage a module to print a price in pretty format, and has imported a method as shown below: import printPrice from '/path/PricePrettyPrint.js'; Based on the code, what must be true about the printPrice function of the PricePrettyPrint module for this import to work?

1. printPrice must be a multi export.

2. printPrice must be the default export.

3. printPrice must be a named export.

4. printPrice must be an ali export.

45. Which statement parses successfully?

1. JSON.parse({'foo'});

2. JSON.parse('foo');

3. JSON.parse('"foo"');

4. JSON.parse("foo");

46. A developer tries to retrieve all cookies, then sets a certain key value pair in the cookie. These statements are used: document.cookie; document.cookie = 'key=John Smith'; What is the behavior?

1. Cookies are read, but the key value is not set because the value is not URL encoded.

2. Cookies are read and the key value is set, and all cookies are wiped.

3. Cookies are read and the key value is set, the remaining cookies are unaffected.

4. Cookies are not read because line 01 should be document.cookies, but the key value is set and all cookies are wiped.

47. A developer is leading the creation of a new browser application that will serve a single page application. The team wants to use a new web framework Minimalist.js. The lead developer wants to advocate for a more seasoned web framework/library that already has a community around it. Which two frameworks/libraries should the lead developer advocate for?

1. React

2. Koa

3. Vue

4. Express

48. What is the primary difference between Array.prototype.forEach and Array.prototype.map?

1. map executes its callback asynchronously, while forEach is synchronous.

2. forEach executes a function for each element but returns undefined, while map returns a new array containing the results of the callback function.

3. map can be used on objects, while forEach is only for arrays.

4. forEach can modify the original array, while map cannot.

49. Given the following code: let x = ('15' + 10) * 2; What is the value of x?

1. 50

2. 1520

3. 3020

4. 35

50. A developer wants to add a CSS class to an element only if it doesn't already have it, and remove it if it does. Which DOM method is best suited for this?

1. element.classList.toggle('my-class')

2. element.classList.contains('my-class')

3. element.classList.add('my-class')

4. element.className += ' my-class'

51. A developer creates a new web server that uses Node.js. It imports a server library that uses events and callbacks for handling server functionality. The server library is made available by a variable named server. The developer wants to log any issues that the server has while booting up. Which code logs an error at boot time with an event?

1. server.catch((error) => { console.log('ERROR', error); });

2. server.on('error', (error) => { console.log('ERROR', error); });

3. try { server.start(); } catch(error) { console.log('ERROR', error); }

4. server.error((error) => { console.log('ERROR', error); });

52. A developer has a requirement to generate SKU numbers that are always 19 characters, starting with 'sku', padded with zeros. Given productSKU = '8475309', which statement creates 'sku0000000008475309'?

1. productSKU = 'sku' + productSKU.padStart(16, '0');

2. productSKU = productSKU.padEnd(16, '0').padStart('sku');

3. productSKU = productSKU.padStart(19, '0').padStart('sku');

4. productSKU = productSKU.padEnd(16, '0').padStart(19, 'sku');

53. A developer creates a Node.js server using a library with events and callbacks. The server variable holds the imported library. Which code logs boot-time errors using events?

1. server.error((error) => { console.log('ERROR', error); });

2. server.on('error', (error) => { console.log('ERROR', error); });

3. try { server.start(); } catch(error) { console.log('ERROR', error); }

4. server.catch((error) => { console.log('ERROR', error); });

FAQs

1. What is the Salesforce Certified JavaScript Developer I certification?

This certification validates your skills in building applications using JavaScript and the Salesforce Lightning Platform. It focuses on JavaScript fundamentals and how they integrate with Salesforce features.

2. How do I get Salesforce Certified JavaScript Developer I certification?

You must pass the Salesforce JavaScript Developer I (CRT-600) exam. It measures your understanding of JavaScript concepts, testing frameworks, and application development on Salesforce.

3. What are the prerequisites for Salesforce Certified JavaScript Developer I?

There are no official prerequisites, but it’s recommended to have basic JavaScript knowledge and experience with Salesforce platform development.

4. How much does the Salesforce JavaScript Developer I exam cost?

The exam costs $200 USD, and retakes are priced at $100 USD, excluding local taxes.

5. What topics are included in the Salesforce JavaScript Developer I exam?

The exam covers topics like Variables, Data Types, Objects, Functions, DOM Manipulation, Event Handling, Asynchronous Programming, and Testing in JavaScript.

6. Is Salesforce JavaScript Developer I certification difficult?

It’s considered moderately challenging, requiring a solid understanding of core JavaScript concepts and how they apply within Salesforce.

7. How long does it take to prepare for Salesforce JavaScript Developer I?

Most candidates take 6–8 weeks of preparation with consistent coding practice, mock exams, and hands-on Salesforce experience.

8. What is the passing score for Salesforce Certified JavaScript Developer I?

You need a 65% score or higher to pass the certification exam.

9. Is Salesforce JavaScript Developer I certification worth it?

Yes. It’s valuable for developers aiming to validate their JavaScript skills and improve job prospects in Salesforce development.

10. What are the best resources to prepare for Salesforce Certified JavaScript Developer I exam?

Use Salesforce Trailhead modules, the official exam guide, and CertiMaan’s exam dumps, mock tests, and practice questions to boost your preparation.