uuidgen stolen by someone else, because there are not enough copies of this line of code :P

uuidgen.js

function uuidgen(){
  return "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx".replace(/[xy]/g,function(a,b){return b = Math.random()*16, (a=="y"? b&3|8: b|0).toString(16)});
}