Classic Object.keys polyfill with a twist: if an object instance of Arguments get into the function, old IEs will simply ignore the for ( k in arguments ) loop and the polyfill will silently fail... The *only way* to identify an object instance of Arguments in old IEs is to check for the presence of the method callee! If an arguments is detected…

object-keys-poly.js

var enumerate = Object.keys || function(o){
        var arr = []
          , o = !!o.callee ? Array.prototype.slice.call(o) : o
          , k
        
        for ( k in o ) if ( arr.hasOwnProperty.call(o, k) )
          arr.push(k)
        
        return arr
    }