1. compress the JS sheet so all the white space is removed.
so rather then

var a;
var b;
var c;
var d;
it appears as

var a;var b;var c;var d;

2. Change all the variables to

a b c.

So rather than
var about
or
var variableName

you change it to
var a
or var i

So if you had a js sheet that looked liked

var about;
var bye;
var cat;
var dog;
var doc=document;
about=document.getElementById("menu");
alert("Hello");
etc...
it would appear as
var a;var b;var c;var d;a=doc.getElementById("menu");alert("Hello");

that way the compression would make a large JS sheet too hard to read or work out. There are online tools that can make this process automatic.