code: function AsyncLoop(iterations, _fn, _successCallback, offset) {
              if (offset === void 0) { offset = 0; }
              this.iterations = iterations;
              this._fn = _fn;
              this._successCallback = _successCallback;
              this.index = offset - 1;
              this._done = false;
          }
docs: Constroctor.
  @param iterations the number of iterations.
  @param _fn the function to run each iteration
  @param _successCallback the callback that will be called upon succesful execution
  @param offset starting offset.