code: function(callback) {
      var a = [];
      for(var i=0; i<this.length; i++) {
        a.push(callback.apply(this.item(i), [i, this.length]));
      }
      return a;
    }
docs: SpahQL#map(callback) -> Array
  - callback (Function): A callback to execute against each result in the set. The callback is exactly as used with #each, but should return a value.
  
  Executes the callback function with each item in this set. The return value from
  each iteration of the callback is appended to an array, which is returned at the end of the loop.