Replace array-mapped variables with the actual variable name/string?

Question

I am trying to edit a Greasemonkey/jQuery script. I can\'t post the link here.
The code is obfuscated and compressed with minify.
It starts like this:

Answer 1

for (var i = 0; i < _0x21e9.length; i++) {
  var funcName = _0x21e9[i];
  _0x21e9[funcName] = funcName;
}

this will add all the function names as keys to the array. allowing you to do

date[_0x21e9["getMonth"]]()