JavaScript Study Guide 2026
Everything you need to pass the JavaScript exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 JavaScript Exam Format at a Glance
📚 JavaScript Topics to Study (33)
✍️ Sample JavaScript Questions & Answers
1. What does `Array.prototype.reduce()` do?
`reduce()` executes a reducer function on each element of the array, accumulating the result into a single output value. It takes a callback and an optional initial value.
2. Which method creates a promise that is already resolved with a given value?
`Promise.resolve(value)` returns a Promise object that is resolved with a given value. If the value is itself a thenable, the returned promise follows that thenable.
3. What is the most important professional competency for JavaScript certification in error handling?
Professional competency requires both deep knowledge of the subject matter and the ability to apply that knowledge in practical situations.
4. In JavaScript practice, what is the best approach to quality improvement in prototypes and classes?
Data-driven quality improvement with measurable outcomes ensures that changes actually produce the intended improvements and can be verified.
5. Which professional attribute is most valued in prototypes and classes within the JavaScript field?
Accountability and commitment to professional standards build trust and ensure consistent, high-quality practice.
6. What does `this` refer to inside an arrow function?
Arrow functions do not have their own `this` binding. Instead, they capture `this` from the surrounding lexical scope at the time they are defined.