3. Functions

The simplest way to set up reusable code in JavaScript is using Functions.

The way you call a function is slightly different from the way you reference variables.

If you define arguments for your function then you can pass different variables as parameters for each call.

JavaScript allows you to pass different numbers of parameters to your function at different times.

Variables inside a function may not exist outside of it.

Functions can have a value that they return back into the code they were called from.

Writing your own library of functions or using such a library written by others will make writing JavaScripts faster.