Master JavaScript from basics to advanced
Arrow functions are the concise ES6 alternative to traditional functions. Learn the syntax, the rules, and the key differences -- no own this, no arguments, no prototype.
Arrow functions are concise and useful, but they are wrong for object methods, constructors, event handlers that need this, and a few other cases. Learn when to reach for a regular function instead.
Rest parameters collect extra function arguments into a real array. Learn how ...args replaces the arguments object with cleaner, more predictable code.
A higher-order function takes or returns another function. Learn the concept, the built-in examples like map and filter, and how to write your own.
Passing a function as an argument is the foundation of callbacks, event handlers, and array methods. Learn the syntax, the patterns, and how to think in functions-as-values.
A function that returns another function is a factory for behavior. Learn how closures make this pattern work and why it is the foundation of configuration, partial application, and encapsulation.
Arrow functions need parentheses around the curly braces to return an object literal. Learn why () => ({ key: value }) works and () => { key: value } does not.
A pure function always returns the same output for the same input and has no side effects. Learn the difference, why purity matters, and how to spot impure code.
Learn practical techniques for writing pure functions in JavaScript. Avoid mutation, isolate side effects, and structure your code so the core logic stays predictable and testable.
Lexical scope means a function's visibility is determined by where it is written, not where it is called. Learn how scope chains work and why nesting matters.
Hoisting is JavaScript's behavior of moving declarations to the top of their scope. Learn how it works for var, let, const, and function declarations -- and the bugs it can cause.
Build a practical event bus using the publish-subscribe pattern in JavaScript. Learn how pub-sub decouples components, enables modular communication, and keeps your codebase clean.
