The Salesforce Certified JavaScript Developer (JS-Dev-101) exam validates your ability to build and maintain JavaScript applications within the Salesforce ecosystem. This certification is designed for developers who work with Salesforce and need to demonstrate proficiency in modern JavaScript practices, from core language fundamentals to server-side implementations. This page provides a clear roadmap of the exam syllabus, question formats, and practical preparation strategies to help you study efficiently and 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 a mix of question types to assess both theoretical knowledge and practical problem-solving ability. Questions progress in difficulty and reflect real-world scenarios you will encounter as a Salesforce Developer.
An effective study plan breaks the syllabus into manageable weekly blocks, combines concept review with hands-on practice, and includes timed mock exams to build confidence and pacing. Dedicate time to each topic area proportionally, with extra focus on asynchronous programming and server-side JavaScript, which often appear heavily on the exam.
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Asynchronous Programming and Server Side JavaScript typically account for a significant portion of the exam, as these are critical skills in real Salesforce projects. Objects, Functions, and Classes also appear frequently because they form the foundation for building maintainable, scalable applications. Allocate study time proportionally to these areas while ensuring you have solid coverage across all seven topic domains.
Variables, Types, and Collections provide the data structures you use throughout your code. Objects and Functions let you organize that data and logic into reusable modules. Browser and Events handle user interactions that trigger your functions. Asynchronous Programming manages long-running operations like API calls without freezing the UI. Server Side JavaScript extends your capabilities to backend services. Testing validates that all these pieces work together correctly in production. Understanding these connections helps you see the exam as a cohesive whole rather than isolated topics.
Ideally, you should have completed at least one or two small projects using JavaScript in a Salesforce context, such as building a Lightning Web Component or a Node.js script that calls Salesforce APIs. Hands-on experience helps you recognize patterns and understand why certain approaches work better than others. If you are new to JavaScript, prioritize coding labs and practice exercises that let you write, run, and debug code before attempting the exam.
Misunderstanding asynchronous execution order and promise chains is a frequent source of lost points. Candidates often confuse variable scope and closure behavior, especially in nested functions and callbacks. Another common error is overlooking error handling best practices or failing to recognize when try-catch blocks are necessary. Review these three areas carefully in your final week, and use the practice test to identify your personal weak spots.
In your final week, shift from learning new material to reinforcing what you have studied. Take a full-length timed practice test to identify any remaining gaps and build exam pacing. Review the explanations for every question you miss, not just the ones you guessed on. Do short, focused review sessions on your weakest topics rather than trying to re-study everything. Get adequate sleep the night before the exam, and avoid cramming new concepts on exam day.
Refer to the code below (assuming Promise.race is intended):
let cat3 = new Promise(resolve =>
setTimeout(resolve, 3000, "Cat 3 completes")
);
Promise.race([cat1, cat2, cat3])
.then(value => {
let result = `${value} the race.`;
})
.catch(err => {
console.log("Race is cancelled:", err);
});
(Assuming cat1 and cat2 are similar to earlier examples: cat2 resolves fastest.)
What is the value of result when Promise.race executes?
From earlier pattern (cars/cats race):
One promise resolves the fastest with 'Car 2 completed' (or analogous 'Cat 2 completes').
Promise.race resolves with the first settled promise's value.
In .then, value is 'Car 2 completed' and:
let result = `${value} the race.`;
// 'Car 2 completed the race.'
Thus result is 'Car 2 completed the race.' option A.
const str = 'Salesforce';
Which two statements result in the word "Sales"?
Comprehensive and Detailed
'Salesforce' indices: S(0) a(1) l(2) e(3) s(4) f(5) ...
A / C (substring(0, 5)):
substring(start, end) returns characters from start up to but not including end.
str.substring(0, 5) characters at indices 0,1,2,3,4 'Sales'.
D (substr(0, 5)):
substr(start, length) returns length characters starting at start.
str.substr(0, 5) 5 chars from index 0 'Sales'.
B is invalid because s is not defined; it should be 0. So the two correct statements are A and D.
Refer to the code below:
let strNumber = '12345';
Which code snippet shows a correct way to convert this string to an integer?
The correct answer is C.
The original option contains a typing error. It should use the existing variable name:
let numberValue = Number(strNumber);
The value of strNumber is a string:
'12345'
Using Number() converts the numeric string into a JavaScript number:
12345
So after execution:
typeof numberValue;
returns:
'number'
Professional review of each option:
Option
Result
Explanation
A
Incorrect
JavaScript does not have a standard global Integer() conversion function.
B
Incorrect
Strings do not have a standard .toInteger() method.
C
Correct
Number(strNumber) correctly converts '12345' into 12345.
D
Incorrect
This is not valid JavaScript casting syntax.
A commonly used alternative would also be:
let numberValue = parseInt(strNumber, 10);
But from the provided answer choices, the verified answer is C.
A developer needs to debug a Node.js web server because a runtime error keeps occurring at one of the endpoints.
The developer wants to test the endpoint on a local machine and make the request against a local server to look at the behavior. In the source code, the server.js file will start the server. The developer wants to debug the Node.js server only using the terminal.
Which command can the developer use to open the CLI debugger in their current terminal window?
(With corrected typing errors: node_inspect node inspect, node_start_inspect node start inspect.)
Node.js includes a built-in command-line (CLI) debugger. To use it directly in the terminal, the standard command is:
node inspect server.js
This:
Starts server.js under the Node.js inspector.
Opens the CLI debugger right in the terminal window where you ran the command.
Lets you interactively:
Step through code
Set breakpoints
Inspect variables
Continue execution, etc.
Why B is correct:
Option B (corrected to node inspect server.js) is exactly the standard Node.js command to run a script under the CLI debugger in the current terminal.
It does not rely on any external GUI tools.
You stay entirely in the terminal to debug.
Why the other options are incorrect:
A . node start inspect server.js
There is no start subcommand like this in standard Node.js CLI.
This is not a valid Node.js debugging command.
C . node server.js --inspect
This starts Node.js with the Inspector protocol enabled and is typically used to connect external tools like Chrome DevTools or VS Code.
It does not open the CLI debugger in the current terminal. Instead, it opens a debugging port that other tools attach to.
The question specifically says ''only using the terminal'' and ''open the CLI debugger in their current terminal window'', which points to node inspect, not --inspect.
D . node -i server.js
-i starts Node in interactive REPL mode, optionally after running a script.
This is for an interactive shell, not the Node debugger.
It does not provide breakpoint/step/next/continue debugging features like the CLI debugger.
Therefore, the only option that opens the Node.js CLI debugger in the current terminal is:
Answe r: B
JavaScript / Node.js knowledge / Study Guide references (concept names only, no links):
Node.js CLI debugger: node inspect <script>
Node.js inspector protocol: node --inspect
Difference between CLI debugger and DevTools-based debugging
Node.js command-line options and subcommands
Refer to the code below:
01 function changeValue(param) {
02 param = 5;
03 }
04 let a = 10;
05 let b = a;
06
07 changeValue(b);
08 const result = a + ' - ' + b;
What is the value of result when the code executes?
We must understand pass-by-value for primitives in JavaScript.
Initial values:
let a = 10;
let b = a; // b gets a copy of the value 10
So:
a is 10
b is 10 (independent copy)
Function call:
changeValue(b);
Function definition:
function changeValue(param) {
param = 5;
}
param receives the value of b, which is 10.
Inside the function, param is a local variable.
param = 5; changes only this local copy.
It does not affect b outside the function.
After the function call:
a is still 10.
b is still 10.
Result:
const result = a + ' - ' + b;
a is 10.
b is 10.
String concatenation: '10 - 10'.
So result is:
'10 - 10'
Therefore, the correct option is:
Study Guide Concepts:
Primitive values (numbers, strings, booleans) are passed by value
Function parameters as local variables
String concatenation with +
Difference between mutating references vs primitives
