Functions JavaScript

 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, you must define it somewhere in the scope from which you wish to call it.

A function definition (also called a function declaration, or function statement) consists of the function keyword, followed by:

The name of the function.

A list of parameters to the function is enclosed in parentheses and separated by commas.

The JavaScript statements that define the function, enclosed in curly brackets, { /* … */ }.

For example, the following code defines a simple function named square:

Declare a function

To declare a function, you use the function keyword, followed by the function name, a list of parameters, and the function body as follows:

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