2.14 Functions

Quite often we need to perform a similar action in many places of the script.

For example, we need to show a nice-looking message when a visitor logs in, logs out and maybe somewhere else.

Functions are the main “building blocks” of the program. They allow the code to be called many times without repetition.

We’ve already seen examples of built-in functions, like alert(message), prompt(message, default) and confirm(question). But we can create functions of our own as well.

Function Declaratioin

To create a function we can use a function declaration.

It looks like this:

function showMessage() {
  alert( 'Hello everyone!' );
}

The function keyword goes first, then goes the name of the function, then a list of parameters in the brackets (empty in the example above) and finally the code of the function, also named “the function body”.