JavaScript ES6+ Fundamentals

• Format — 1,200+ MCQs with instant explanations on every wrong answer
• Duration — about 14.2 hours of focused practice
• Level — intermediate; assumes basic JavaScript (variables, functions, objects)
• Cost — free with Abekus Pro, otherwise paid in credits with Abekus Pro, otherwise paid in credits; with a completion certificate
• Audience — developers modernizing their JavaScript, placement candidates, and React or Node.js learners solidifying their syntax foundation
• Part of — the JavaScript Mastery series on Abekus

Three audiences get the most from this course. Developers who learned JavaScript before ES6 became standard — you know the old syntax, you have picked up pieces of the new syntax by copying examples, but you have not drilled the actual mechanics: when does an arrow function break? what exactly does the Temporal Dead Zone prevent? how does module scope differ from function scope? Students preparing for modern JavaScript interviews where ES6+ knowledge is tested directly — destructuring, spread/rest, Symbols, and module behavior are all fair game. And learners working through React or Node.js who keep running into ES6+ syntax they half-understand — this course covers the exact feature set both frameworks lean on.

Core ES6 syntax

• Variables & Scope — let vs const vs var, the Temporal Dead Zone and why it exists, closures and how the scope chain resolves names
• Arrow Functions & this Binding — arrow function syntax, how arrow functions inherit this lexically instead of binding it dynamically, and where arrow functions cannot substitute for regular functions
• Template Literals & Tagged Templates — expression interpolation, multiline strings, tagged template syntax, and edge cases in how interpolated expressions are coerced
• Destructuring — array and object destructuring, nested patterns, default values, renaming on destructure, and function parameter destructuring
• Rest & Spread Operators — rest parameters vs the arguments object, spread in function calls, array literals, and object literals, and the edge cases that trip up developers switching between them

Functions, classes, and modules

• Default Parameters & Function Enhancements — default parameter evaluation order, function metadata (name and length), method shorthand syntax, and computed property names
• Classes & Inheritance — class syntax and how it maps to the prototype chain, static vs instance members, extends and super, and where classes behave differently from constructor functions
• Modules — named and default exports, import syntax, module scope behavior (strict by default, single instance per runtime), and dynamic import() for code splitting

Objects, built-ins, and advanced features

• Enhanced Object Literals & Object Methods — shorthand properties, computed keys, Object.assign, Object.entries, Object.fromEntries, and property descriptors
• New Array & String Methods — ES6 additions (find, findIndex, Array.from), ES2019-2023 additions (flat, flatMap, at), and new String methods (padStart, trimStart, replaceAll)
• Symbols — Symbol creation, uniqueness guarantees, well-known Symbols (Symbol.iterator, Symbol.toPrimitive), and using Symbols as non-enumerable property keys
• ES6+ Mastery — side-by-side comparisons of every ES6+ feature against its ES5 equivalent, pattern selection, and real-world application contexts

ES5 JavaScript was written with var, prototype-based construction, string concatenation, and script tags with global leakage. ES6 replaced almost all of it: let/const for declarations, class syntax for object construction, template literals for string building, and native ES Modules for code organisation. The changes are not cosmetic — let/const have different scoping rules than var, class syntax exposes and hides prototype mechanics in specific ways, and ES Modules are statically analysable in a way CommonJS require() is not. Understanding why each feature was designed the way it was makes the edge cases predictable rather than surprising.

The trap with ES6+ is that most of the syntax is easy to copy-paste correctly without understanding it. You can use arrow functions for months without knowing why they break as event handlers or object methods. You can use destructuring without knowing what happens with nested undefined values. MCQ practice forces you to confront those edge cases directly — not by reading about them, but by being wrong about them once, reading the explanation, and not being wrong about them again. Work through topics in order the first time; once you have the mental model, use the subtopic drill to hammer specific edge cases before an interview.

Each question is mapped to a specific subtopic — for example, "Arrow Function Limitations" or "Advanced Destructuring" — so the system tracks exactly which features you understand and which you are pattern-matching without understanding. An AI guide surfaces the weakest areas. You can work through the full course in order or jump to a subtopic to fill a known gap before a project or interview.

1,278 questions at roughly 40 seconds each works out to about 14.2 hours of focused practice. Most learners cover this in 3–4 weeks at 30–45 minutes per session. If you are preparing for an interview and need to prioritise, the highest-yield topics for ES6+ questions are Destructuring, Arrow Functions & this Binding, Modules, and Classes & Inheritance — together about 500 questions covering the features most commonly tested in screening rounds.

This course is Part 2 of the JavaScript Mastery series on Abekus. If you have not completed Part 1 — the core JavaScript Fundamentals course covering types, closures, prototypes, and the event loop — that is the recommended starting point. After this course, React Fundamentals is the natural next step: React's component model, hooks, and JSX lean directly on the arrow functions, destructuring, modules, and class syntax covered here. Node.js similarly assumes ES6+ module and async syntax fluency.