javascript-mastery

Topics in the source

• 🧠 JavaScript Mastery
• When to Use This Skill
• 1. Fundamentals
• 1.1 Primitive Types
• 1.2 Type Coercion
• 1.3 Equality Operators
• 2. Scope & Closures
• 2.1 Scope Types

33+ essential JavaScript concepts every developer should know, inspired by 33-js-concepts. Use this skill when: Explaining JavaScript concepts Debugging tricky JS behavior Teaching JavaScript fundamentals Reviewing code for JS best practices Understanding language quirks -- JavaScript has 7 primitive types: Key points: Primitives are immutable Passed by value typeof null === "object" is a historical bug JavaScript implicitly converts types: Falsy values (8 total): false, 0, -0, 0n, "", null, undefined, NaN Rule: Always use === unless you have a specific reason not to. -- A closure is a function that remembers its lexical scope: Common use cases: Data privacy (module pattern) Function factories Partial application Memoization -- Stack overflow example: -- Execution order: 1. Synchronous code (call stack) 2. Microtasks (Promise callbacks, queueMicrotask) 3. Macrotasks (setTimeout, setInterval, I/O) -- Functions that take or return functions: -- -- -- | Concept | Key Point | | :------------- | :-------------------------------- | | == vs === | Always use === | | var vs let | Prefer let/const | | Closures | Function + lexical scope | | this | Depends on how function is called | | Event

This is an excerpt. Refer to the complete source and its current requirements.