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 Declaration
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 between the parentheses (comma-separated, empty in the example above, we’ll see examples later) and finally the code of the function, also named “the function body”, between curly braces.
function name(parameter1, parameter2, ... parameterN) {
// body
}Our new function can be called by its name: showMessage().
For instance: