100+ Free Certified Associate JavaScript Programmer Practice Questions

Classless Objects

Create individual objects with literals; add, modify, and delete properties using dot and bracket notation; check existence with in and enumerate with Object.keys/values/entries; compare, copy, and deep-clone objects; define getters/setters; configure mutability with defineProperty, preventExtensions, seal, and freeze; and build classless objects with factories, constructor functions, Object.create, and prototypes via setPrototypeOf.

Classes and the Class-Based Approach

Declare classes and class expressions; instantiate with new and verify with instanceof; initialize class fields and private fields; expose computed state with get and set accessors; implement inheritance with extends and call parent logic with super; define static methods and properties; and relate class syntax to constructor functions and prototype methods.

Built-in Objects

Work with Number formatting and conversion; String operations like slice, split, replace, pad, and trim; Date construction and elapsed-time measurement; Arrays with slice/splice/spread and functional methods find, every, some, filter, sort, map, and reduce; Set and Map collections; objects as dictionaries; JSON.stringify and JSON.parse; Math methods; and regular expressions with test, exec, match, search, and replace.

Advanced Functions

Use default values, rest parameters, and spread; leverage closures and IIFEs over the lexical environment; manage this with call, apply, and bind; compose decorators and higher-order functions; define generators and custom iterators; and handle asynchronous flows with callbacks, promises (then/catch/finally, all/any/race), async/await with try/catch, and network requests via XMLHttpRequest and the Fetch API.