Salesforce JavaScript Developer I (JS-Dev-101) Exam Guide – Winter ’26 | Syllabus + Questions
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Updated for Winter '26 Release
Last Updated: November 2025 | Exam Version: Winter '26
This guide covers the Salesforce Certified JavaScript Developer I (JS-Dev-101) exam – including the latest structure, objectives, and focus areas around modern JavaScript, asynchronous programming, and testing. The exam is still language-centric, not Salesforce-specific, and pairs with the Lightning Web Components Specialist superbadge for the full credential.
💻 What is Salesforce JavaScript Developer I?
Validates your ability to write and reason about vanilla JavaScript on both browser and server – arrays, objects, classes, async/await, promises, events, error handling, and testing fundamentals.
The exam is not tied to LWC or a specific framework. It focuses on JavaScript language features that apply to any modern front-end or Node.js environment, which then translate naturally to building Lightning Web Components. :contentReference[oaicite:0]{index=0}
Together with the LWC Specialist superbadge, it forms the full JavaScript Developer I credential and is a great foundation for Salesforce front-end developer and LWC-heavy Platform Developer roles. :contentReference[oaicite:1]{index=1}
Salesforce Certified JavaScript Developer I (JS-Dev-101)
Exam guide for web developers and Salesforce developers who want to validate their JavaScript fundamentals.
Ideal for candidates with 1–2 years of JavaScript experience and solid hands-on practice with modern web development. :contentReference[oaicite:2]{index=2}
📊 JavaScript Developer I Exam at a Glance
📝 Note: Official exam details: 60 multiple-choice/multiple-select questions, 105 minutes, 65% passing score, exam fee $200, retake fee $100. Always confirm the latest values on the official exam guide before scheduling. :contentReference[oaicite:3]{index=3}
🔗 How the JavaScript Developer I Credential Works
To earn the full Salesforce Certified JavaScript Developer I credential, you typically complete:
- The proctored JavaScript Developer I multiple-choice exam (JS-Dev-101)
- The Lightning Web Components Specialist superbadge on Trailhead
These two parts can usually be completed in any order. Once both are done, Salesforce awards the full JavaScript Developer I credential. :contentReference[oaicite:4]{index=4}
Exam Objectives & Weightage (JavaScript Developer I)
1. Variables, Types & Collections
23%Master the fundamentals: variables, scopes, primitive types, arrays, objects, JSON and how JavaScript treats truthy/falsey values and type coercion. This is a high-weight section for the exam. :contentReference[oaicite:5]{index=5}
2. Objects, Functions & Classes
25%
Deep dive into object literals, prototypes, this, arrow functions vs regular functions, higher-order functions, ES6
classes and modules. You’ll read and reason about a lot of code in this domain. :contentReference[oaicite:6]{index=6}
3. Browser & Events
17%Covers DOM manipulation, event listeners, event propagation, browser APIs and using developer tools to inspect and debug behavior. :contentReference[oaicite:7]{index=7}
4. Debugging & Error Handling
7%
Using try/catch, error objects, console APIs, breakpoints and the debugger to track down issues and handle failures
gracefully. :contentReference[oaicite:8]{index=8}
5. Asynchronous Programming
13%
Promises, async/await, callbacks, the event loop, task queue and how JavaScript schedules work. Expect several questions
on order of execution and async flow. :contentReference[oaicite:9]{index=9}
6. Server-Side JavaScript
8%Platform-agnostic topics like Node-style modules, server-side execution, and how JavaScript works outside the browser. :contentReference[oaicite:10]{index=10}
7. Testing
7%General JavaScript testing concepts: unit tests, assertions, mocking, and test structure – not tied to a specific testing framework. :contentReference[oaicite:11]{index=11}
📝 Sample JavaScript Developer I Questions
💡 Code-Reading & Scenario-Based Practice
Most questions show a short code snippet or real-world scenario. Try to mentally execute the code and pay special attention to scope, hoisting, async behavior, and type coercion.
Question 1: Variables & Scope
function test() {
var x = 1;
if (true) {
let x = 2;
console.log('inside:', x);
}
console.log('outside:', x);
}
test();
What is printed to the console?
A) inside: 2 then outside: 2
B) inside: 1 then outside: 1
C) inside: 2 then outside: 1
D) inside: undefined then outside: 1
✓ Correct Answer: C) inside: 2 then outside: 1
Explanation: let is block-scoped. Inside the if, a new x shadows the outer var x.
Outside the block, the original x is still 1.
Question 2: Type Coercion
console.log(1 + "2" + 3); console.log(1 + 2 + "3");
What is logged by these two statements?
A) "123" and "33"
B) "6" and "6"
C) "16" and "16"
D) "13" and "13"
✓ Correct Answer: A) "123" and "33"
Explanation: In 1 + "2" + 3, 1 is coerced to a string: "1" + "2" = "12", then "12" + 3 = "123".
In 1 + 2 + "3", the first operation is numeric (3), then 3 + "3" becomes the string "33".
Question 3: Async / Await
async function getData() {
return "done";
}
console.log(getData());
What does this code log?
A) "done"
B) Promise { "done" } (or similar)
C) undefined
D) A runtime error
✓ Correct Answer: B) Promise { "done" } (or similar)
Explanation: An async function always returns a Promise. Here, return "done" becomes
Promise.resolve("done"), so logging the function call prints a Promise object, not the string value.
Question 4: Array Methods
const nums = [1, 2, 3, 4]; const result = nums .filter(n => n % 2 === 0) .map(n => n * 2) .reduce((sum, n) => sum + n, 0); console.log(result);
What is logged to the console?
A) 0
B) 6
C) 12
D) 20
✓ Correct Answer: C) 12
Explanation: filter keeps even numbers → [2, 4]. map doubles them → [4, 8].
reduce sums them with initial 0 → 4 + 8 = 12.
Question 5: Error Handling
try {
JSON.parse("{ invalid }");
console.log("parsed");
} catch (e) {
console.log("error");
} finally {
console.log("finally");
}
What is printed?
A) parsed
B) error
C) error then finally
D) parsed then finally
✓ Correct Answer: C) error then finally
Explanation: JSON.parse throws, so the console.log("parsed") line is skipped.
Control jumps to catch (error), then the finally block runs regardless.
💡 Exam Tip: Many questions probe subtle JavaScript behavior (hoisting, coercion, async execution). Slow down and mentally run the code on a small example before choosing your answer.
❓ Salesforce JavaScript Developer I (JS-Dev-101) FAQ
Check the official Salesforce certification page for current prerequisites. Most certifications recommend having relevant hands-on experience (typically 6-12 months) with the specific Salesforce product or feature area.
General recommendations:
- Complete relevant Trailhead trails and superbadges
- Get hands-on experience in a Developer Edition org
- Review the official exam guide thoroughly
- Complete practice exams and aim for 80%+ consistently
Recommended preparation steps:
- Study the exam guide: Review all exam objectives and weightage carefully
- Complete Trailhead: Finish all recommended trails and superbadges for this certification
- Hands-on practice: Use a Developer Edition org to practice the features and scenarios covered in the exam
- Practice exams: Take multiple practice exams and aim for 80%+ consistently
- Review release notes: Study Winter '26 release notes for new features that may appear in exam questions
- Focus on weak areas: Use exam weightage to prioritize study time on higher-weighted domains
Refer to the "Exam Objectives & Weightage" section above for detailed topic breakdown. The exam covers multiple domains with varying weightage. Focus more study time on domains with higher percentages.
Pro tip: Review the exam guide's domain breakdown carefully and ensure you have hands-on experience with all topics, especially those with higher weightage.
Preparation time varies based on your background and experience:
- With relevant experience: 2-3 months of focused study (10-15 hours per week)
- Without experience: 4-6 months of dedicated study (15-20 hours per week)
- With similar certifications: 1-2 months if you have related credentials
Best practice: Don't schedule your exam until you're consistently scoring 80%+ on practice tests and feel confident about all exam domains.
Most Salesforce certification exams require a passing score of 65-68%. The exact passing score is not disclosed by Salesforce and may vary slightly by exam version.
Important: Salesforce uses a scaled scoring system, meaning not all questions have equal weight. Focus on understanding all domains thoroughly rather than memorizing specific answers.
Strategy: Aim to score consistently above 80% on practice exams before scheduling your real exam to ensure a comfortable passing margin.
💡 Exam Success Tips
📚 Study the Exam Guide
Review the official exam guide thoroughly. Understand each domain's weightage and prioritize higher-weighted topics during your final review.
🛠️ Hands-On Practice
Use a Developer Edition org to practice all features covered in the exam. Real hands-on experience is invaluable for scenario-based questions.
📝 Practice Exams
Take multiple practice exams and aim for 80%+ consistently. Understand WHY answers are correct, not just memorizing them.
🆕 Review Release Notes
Study Winter '26 release notes. New features often appear in exam questions. This guide highlights key Winter '26 updates.
⏱️ Time Management
Manage your time during the exam. Flag difficult questions and return to them later. Ensure you answer all questions before time runs out.
🎯 Focus on Weak Areas
Review practice exam results and dedicate extra study time to domains where you scored lower. Use exam weightage to prioritize.
📚 Study Plan for JavaScript Developer I (3–6 Weeks)
🎯 Suggested Roadmap
Review variables, types, arrays, objects, functions, classes using MDN and Trailhead modules. Practice small exercises daily (no frameworks).
Build small pages that manipulate the DOM, handle events and use DevTools (breakpoints, Call Stack, Network). Focus on understanding event propagation and default behavior.
Practice promises, async/await, fetch, timeouts and executing JS on Node. Draw diagrams to see the event loop, microtasks and macrotasks in action.
Learn basic JS testing concepts, then apply your JS skills in Lightning Web Components and complete practice exams in timed conditions.
💡 Exam Day Tips (JavaScript Developer I)
60 questions in 105 minutes ≈ ~1.75 minutes per question. If a code snippet looks long, skim the question first, then scan the code for the specific behavior being tested.
The exam often tests spec-accurate behavior. Avoid answers that rely on “magic” or non-standard behavior; think in terms of what the JavaScript engine actually does.
Many questions have 2 “okay” answers. Remove options that break scope rules, async semantics, or clearly misuse features (e.g., blocking async code) and then pick the most idiomatic one.
❓ JavaScript Developer I – Frequently Asked Questions (FAQ)
Is this exam about Lightning Web Components or pure JavaScript?
The exam focuses on core, framework-agnostic JavaScript: variables, objects, async programming, browser APIs, and testing concepts. LWC knowledge helps you relate concepts, but the questions are about JavaScript itself, not LWC syntax. :contentReference[oaicite:12]{index=12}
Do I need prior Salesforce experience to pass this exam?
Not strictly. Many candidates come from a web development background and use this cert as a gateway into the Salesforce ecosystem. Salesforce experience helps when later applying these skills in LWC or platform projects. :contentReference[oaicite:13]{index=13}
How hard is JavaScript Developer I compared to Platform Developer I?
Many developers find it conceptually deeper in JavaScript but narrower in scope than PD1. PD1 mixes Apex, Flows, and platform topics, while JS Dev I dives into language details like scope, coercion, async and the event loop.
Do I need to complete the LWC Specialist superbadge to be certified?
Yes, Salesforce typically requires both the JavaScript Developer I exam and the Lightning Web Components Specialist superbadge to award the full credential. Check the official certification page for the most up-to-date requirements. :contentReference[oaicite:14]{index=14}
How much JavaScript experience should I have before taking the exam?
Salesforce and community guidance suggest around 1–2 years of hands-on JavaScript experience, including building real applications and understanding ES6+ features, async patterns, and browser APIs. :contentReference[oaicite:15]{index=15}
How long is the JavaScript Developer I certification valid?
Salesforce certifications remain valid as long as you complete required maintenance modules on Trailhead when prompted. You’ll receive email reminders in advance when a maintenance module is due.