JavaScript

Closure

Definition

A function that retains access to variables from its outer (enclosing) scope even after the outer function has returned. Closures are created every time a function is created in JavaScript.

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Related Terms

Scope

The region of code where a variable is accessible. JavaScript has global scope, function scope, and block scope. Block scope was introduced with let and const in ES6.

Higher-Order Function

A function that either takes one or more functions as arguments, returns a function, or both. Common examples include map, filter, reduce, and forEach.

IIFE

Immediately Invoked Function Expression — a function that runs immediately after being defined. IIFEs create a private scope and are used to avoid polluting the global namespace.