Agent skill · writing content · aiskillstore
javascript-mastery
Comprehensive JavaScript reference covering 33+ essential concepts every developer should know. From fundamentals like primitives and closures to advanced patterns like async/await and functional programming. Use when explaining JS concepts, debugging JavaScript issues, or teaching JavaScript fundamentals.
Why this skill is useful
Codifies JavaScript best practices and common concepts but lacks niche or executable content.
What it needs
About 8k tokens when loaded. Last updated 2026-08-07. 405 stars on the source repository.
What this skill does
🧠 JavaScript Mastery 33+ essential JavaScript concepts every developer should know, inspired by 33-js-concepts. When to Use This Skill Use this skill when: Explaining JavaScript concepts Debugging tricky JS behavior Teaching JavaScript fundamentals Reviewing code for JS best practices Understanding language quirks --- 1. Fundamentals 1.1 Primitive Types JavaScript has 7 primitive types: Key points: Primitives are immutable Passed by value typeof null === "object" is a historical bug 1.2 Type Coercion JavaScript implicitly converts types: Falsy values (8 total): false, 0, -0, 0n, "", null, undefined, NaN 1.3 Equality Operators Rule: Always use === unless you have a specific reason not to. --- 2. Scope & Closures 2.1 Scope Types 2.2 Closures A closure is a function that remembers its lexical scope: Common use cases: Data privacy (module pattern) Function factories Partial application Memoization 2.3 var vs let vs const --- 3. Functions & Execution 3.1 Call Stack Stack overflow example: 3.2 Hoisting 3.3 this Keyword --- 4. Event Loop & Async 4.1 Event Loop Execution order: 1. Synchronous code (call stack) 2. Microtasks (Promise callbacks, queueMicrotask) 3. Macrotasks (setTimeout, setInterval, I/O) 4.2 Callbacks 4.3 Promises 4.4 async/await --- 5. Functional Programming 5.1 Higher-Order Functions Functions that take or return functions: 5.2 Pure Functions 5.3 map, filter, reduce 5.4 Currying & Composition --- 6. Objects & Prototypes 6.1 Prototypal Inheritance 6.2 Object Methods --- 7. …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills aiskillstore/javascript-mastery