code: function () {
              if ( this._isComplete ) return;
      
              //IE
              if ( this.script.readyState ) {
                  this.script.onreadystatechange = $B.bind( function (e) {
                      if ( this.script.readyState === 'loaded' || this.script.readyState === 'complete' ) {
                          this._removeEvents();
                          this._isComplete = true;
                          this.dispatch( 'load', {target: this, script: this.script, data: this._data} );
                      }
                  }, this);
              } else {
                  this.script.onload = $B.bind( function (e) {
                      this._removeEvents();
                      this._isComplete = true;
                      this.dispatch( 'load', {target: this, script: this.script, data: this._data} );
                  }, this);
              }
      
              this.script.src = this._path;
              document.getElementsByTagName( 'head' )[0].appendChild( this.script );
          }
docs: Load 시작, 로드가 진행중이면 unload시킨후 로드해야 한다. 로드완료후 호출 불가능.