docs: function(eachFn) {
      // Force compiler to respect argument length.
      var argLen = arguments.length, context = arguments[1];
      var length = this.length, index = 0;
      assertCallable(eachFn);
      while(index < length) {
        if (index in this) {
          eachFn.call(context, this[index], index, this);
        }
        index++;
      }
    }