The JS-Dev-101 exam validates your ability to build and maintain JavaScript solutions within the Salesforce ecosystem. This certification, formally known as Salesforce Certified JavaScript Developer, is designed for developers who work with Salesforce and need to demonstrate proficiency in modern JavaScript practices. Whether you're advancing your Salesforce Developer credentials or specializing in front-end and server-side JavaScript development, this exam measures both foundational knowledge and practical problem-solving skills. This page provides a structured study roadmap, topic breakdown, and preparation strategies to help you pass with confidence.
Use this topic map to guide your study for Salesforce JS-Dev-101 (Salesforce Certified JavaScript Developer) within the Salesforce Developer path.
The JS-Dev-101 exam uses multiple question types to assess both conceptual understanding and the ability to apply JavaScript in real Salesforce scenarios. Questions progress in difficulty and require you to think critically about code behavior and best practices.
Questions emphasize practical application, so studying with real code examples and hands-on practice is essential to success.
A structured study plan spread over 4-6 weeks allows you to build depth in each topic area without overwhelming yourself. Start with foundational concepts, move into practical application, and finish with full-length practice tests under timed conditions.
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Focus first on Asynchronous Programming, Objects and Functions, and Testing, as these topics appear frequently on the exam and are critical to real-world Salesforce development. Variables and Types form the foundation, so ensure you understand them before moving to more complex topics. Allocate your remaining time to Browser and Events, and Server Side JavaScript based on your current role and experience.
Variables store data using JavaScript's type system, and Collections (arrays and objects) hold multiple values that you then manipulate with Functions. In a real project, you might declare a const array of user objects, iterate through them with a function, and return filtered results. Understanding how these layers work together is essential for writing clean, maintainable code in Salesforce applications.
Write small programs that combine multiple topics: for example, create a function that fetches data asynchronously, handles errors with try-catch, updates the DOM with the results, and includes unit tests. Use the browser console and Node.js to test your code. Building real mini-projects reinforces concepts far better than reading alone and builds the muscle memory needed for scenario-based questions.
Candidates often confuse var, let, and const scoping rules, misunderstand how async/await differs from Promises, or overlook event delegation in DOM manipulation. Others rush through questions without carefully reading code snippets, leading to careless errors. Take time to trace through code mentally, test your assumptions in a console, and read each question fully before selecting an answer.
Dedicate 3-4 days to a full-length timed practice test, review all incorrect answers, and identify patterns in your weak areas. Spend the remaining days doing targeted review on those weak topics using both study materials and hands-on coding. On the final day, do a light review of key definitions and concepts, but avoid cramming new material. Get good sleep before the exam and trust your preparation.
A developer needs the function personalizeWebsiteContent to run when the webpage is fully loaded (HTML and all external resources).
Which implementation should be used?
JavaScript defines two main page-loading events:
DOMContentLoaded
Fires when the HTML document has been completely parsed.
External resources like images, stylesheets, iframe contents, etc. may not be loaded yet.
load event on window
Fires when:
HTML is fully parsed
All dependent resources (images, scripts, CSS, fonts, etc.) are fully loaded
The requirement states:
''when the webpage is fully loaded (HTML content and all related files)''
This aligns exactly with the window load event.
Implementation:
window.addEventListener('load', personalizeWebsiteContent);
This matches option B.
JavaScript knowledge references (text-only)
DOMContentLoaded fires after HTML parsing only.
load fires after all page resources finish loading.
The window object is the correct target for listening to the full load event.
Refer to the code snippet:
01 let array = [1, 2, 3, 4, 4, 5, 4, 4];
02 for (let i = 0; i < array.length; i++) {
03 if (array[i] === 4) {
04 array.splice(i, 1);
05 i--;
06 }
07 }
What is the value of array after the code executes?
Comprehensive and Detailed
The loop removes every 4:
Start: [1, 2, 3, 4, 4, 5, 4, 4]
i=0 1 (no change)
i=1 2 (no change)
i=2 3 (no change)
i=3 4 splice removes index 3 [1,2,3,4,5,4,4], then i-- 2
Next loop, i=3 4 again splice [1,2,3,5,4,4], i-- 2
i=3 5 (no change)
i=4 4 splice [1,2,3,5,4], i-- 3
i=4 4 splice [1,2,3,5], i-- 3
Next i=4, array.length is 4 loop ends.
All 4s removed, final array: [1, 2, 3, 5].
Given the JavaScript below:
01 function filterDOM(searchString){
02 const parsedSearchString = searchString && searchString.toLowerCase();
03 document.querySelectorAll('.account').forEach(account => {
04 const accountName = account.innerHTML.toLowerCase();
05 account.style.display = accountName.includes(parsedSearchString) ? /* Insert code here */;
06 });
07 }
Which code should replace the placeholder comment on line 05 to hide accounts that do not match the search string?
We have a ternary:
account.style.display = accountName.includes(parsedSearchString)
? /* if true */
: /* if false */;
Requirement:
If the account matches the search string show it.
If it does not match hide it.
For display:
Show: 'block' (or similar visible value).
Hide: 'none'.
So we want:
account.style.display = accountName.includes(parsedSearchString)
? 'block'
: 'none';
That corresponds to option A.
Why others are wrong:
B, C use values suitable for visibility, not display.
D ('none' : 'block') inverts the logic, hiding matches and showing non-matches.
Refer to the following code:
The answer choices appear to belong to an event propagation question using nested elements such as an outer element and an inner element.
The important clue is this third argument:
addEventListener('click', handlerFunction, true);
When the third argument is true, the event listener runs during the capturing phase.
In event capturing, the browser handles the event from the outside toward the inside:
Outer element Inner element
So, if an inner element is clicked and both the outer and inner elements have click listeners registered with capture mode set to true, the outer listener runs first, then the inner listener runs.
That produces:
Outer message
Inner message
So the matching option is B.
Important correction:
In the exact code shown, the buttons are sibling elements:
<button class='secondary'>Save draft</button>
<button class='primary'>Save and close</button>
They are not nested inside one another. Therefore, with the code exactly as written:
Clicking the secondary button logs:
Save message.
Clicking the primary button logs:
Success message.
However, because the provided answer choices refer to Outer message and Inner message, the intended concept is clearly event capturing. In a capturing-phase question with nested outer and inner elements, the correct order is:
Outer message
Inner message
Therefore, the verified answer for the intended event-capturing question is B.
Corrected code:
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 result after line 10 executes?
The verified answer is A.
This constructor function runs when new Person() is called:
function Person() {
this.firstName = 'John';
}
So this line:
const myFather = new Person();
creates an object like this:
{
firstName: 'John'
}
Then the prototype is assigned a method named job:
Person.prototype = {
job: x => 'Developer'
};
Because myFather is created from Person, it can access properties and methods from Person.prototype.
So:
myFather.firstName
returns:
'John'
And:
myFather.job()
returns:
'Developer'
Therefore:
const result = myFather.firstName + ' ' + myFather.job();
becomes:
const result = 'John' + ' ' + 'Developer';
Final value:
'John Developer'
Option B is incorrect because job() returns 'Developer', not undefined.
Option C is incorrect because job exists on Person.prototype, so it is callable.
Option D is incorrect because firstName is assigned inside the constructor.
Therefore, the verified answer is A.
