Static analysis: tell if two Javascript functions are the same

I am looking for a way using static analysis of two JavaScript functions to determine if they are the same. Let me define a few definitions of "the same."

Level 1: . The functions are the same, with the exception of possible different spaces, for example. TABS, CR, LF and SPACES.

Level 2 Functions may have different spaces, such as level 1, but may also have different variable names.

Level 3

For the first level, I think I could just remove all (non-literal, which can be hard) spaces from each line containing two JS function definitions, and then compare the lines.

For the second level, I think I will need to use something like the SpiderMonkey parser to create two parsing trees, and then write a comparer that walks the trees and allows the variables to have different names.

[Edit] William makes a good point below. I mean the same thing. Now I am looking for some practical strategies, especially regarding the use of parsing trees.