When you check out the source code you will find that their is an encoded string ‘%69%6C%6F%76%65%6D%6F%6F‘ and the variable moo has its decoded word i.e. our answer.
The easiest way to decode this string is write alert (moo); just above the function and run this script. You can do it by two ways, either save the code in another file and then run it in your browser or use firebug(developer tool) and edit the script tag then and there and see the magic.
Answer: In case you don’t want to try it yourself, answer is ilovemoo.