A JavaScript function is defined with the function keyword, followed by a name, followed by parentheses (). Function names can contain letters, digits, underscores, and dollar signs (same rules as variables).

Jul 8, 2025 · Functions are one of the fundamental building blocks in JavaScript. A function in JavaScript is similar to a procedure—a set of statements that performs a task or calculates a value, but for a procedure to qualify as a function, it should take some input and return an output where there is some obvious relationship between the input and the output. To use a function, …

JavaScript functions are defined with the function keyword. You can use a function declaration or a function expression.

Jul 15, 2025 · The function* declaration creates a binding of a new generator function to a given name. A generator function can be exited and later re-entered, with its context (variable bindings) saved across re-entrances.

Jun 28, 2025 · Functions in JavaScript are reusable blocks of code designed to perform specific tasks. They allow you to organize, reuse, and modularize code. It can take inputs, perform actions, and return outputs.

Summary Use the function keyword to declare a function. Use the functionName() to call a function. All functions implicitly return undefined if they don’t explicitly return a value. Use the return statement to return a value from a function explicitly. The arguments variable is an array-like object inside a function, representing function ...

Oct 14, 2022 · The function keyword goes first, then goes the name of the function, then a list of parameters between the parentheses (comma-separated, empty in the example above, we’ll see examples later) and finally the code of the function, also …

Description The function statement declares a function. A declared function is "saved for later use", and will be executed later, when it is invoked (called). In JavaScript, functions are objects, and they have both properties and methods. A function can also be defined using an expression (See Function Definitions). Read our JavaScript Tutorial to learn all you need to know about …

Jul 9, 2025 · The JavaScript language has many built-in functions to allow you to do useful things without having to write all that code yourself. In fact, some of the code you are calling when you invoke (a fancy word for run, or execute) a built-in browser function couldn't be written in JavaScript — many of these functions are calling parts of the background browser code, which …

A function is an independent block of code that performs a specific task. A function expression is a way to store functions in variables. In this tutorial, you will learn about JavaScript functions and function expressions with the help of examples.