kb/data/developer.mozilla.org/en-US/docs/Glossary/Function-0.md

title	chunk	source	category	tags	date_saved	instance
Function - Glossary | MDN	1/3	https://developer.mozilla.org/en-US/docs/Glossary/Function	reference	web, html, css, javascript, documentation	2026-05-05T05:32:08.608917+00:00	kb-cron

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1. Glossary
2. Function

Function

A function is a code snippet that can be called by other code or by itself, or a variable that refers to the function. When a function is called, arguments are passed to the function as input, and the function can optionally return a value. A function in JavaScript is also an object. A function name is an identifier included as part of a function declaration or function expression. The function name's scope depends on whether the function name is a declaration or expression.

In this article

• Different types of functions
• See also

Different types of functions

An anonymous function is a function without a function name. Only function expressions can be anonymous, function declarations must have a name: The following terms are not used in the ECMAScript language specification, they're jargon used to refer to different types of functions. A named function is a function with a function name: An inner function is a function inside another function (square in this case). An outer function is a function containing a function (addSquares in this case): A recursive function is a function that calls itself. See recursion. An Immediately Invoked Function Expression (IIFE) is a function that is called directly after the function is loaded into the browser's compiler. The way to identify an IIFE is by locating the extra left and right parenthesis at the end of the function's definition. Function expressions, named or anonymous, can be called immediately. Declared functions can't be called immediately this way, because IIFEs must be function expressions. If you'd like to know more about IIFEs, check out the following page on Wikipedia: Immediately Invoked Function Expression

See also

• Functions
• Arrow Functions