function changecolor(code) {
document.bgColor=code
}

This page is an excellent example of one function being used by several buttons in the same document. Our function is called changecolor(code). It has only one line:
document.bgColor=code.

You probably guessed that bgColor stands for background color.
If I type document.bgColor="red" the background will turn red.

By writing the command document.bgColor=code I am allowing myself to define the variable code as any color I want.

Later, in the form. I define a button with the command:
onClick="changecolor('green')"

onClick="changecolor('green')" is telling the program 2 things:

1. Run the funtion named changecolor(code).
2. code='green'

Next Chapter