I did have a look at tern. It looks very interesting. But it couldn't rename the field with this code:

    var key = "test";
    var theThing = {};
    theThing[key] = function() { return "hello"; };;
    console.log(theThing.test());

Which isn't so exotic.

To clarify, if I had a string in my source code that had nothing to do with looking up attributes, it wouldn't be touched?

    var one = "_I_just_like_talking_like_this_";
    var two = "_two";
    var test = {};
    test[two] = "II";
    console.log(test._two);

The result would be

    var one = "_I_just_like_talking_like_this_";
    var two = "two";
    var test = {};
    test[two] = "II";
    console.log(test.two);


?