code: function() {
          var map = this._map,
              heatmap = this.gl,
              data = this.data,
              dataLen = data.length,
              floor = Math.floor,
              scaleFn = this['_scale' + this.options.units].bind( this ),
              multiply = this._multiply;
  
          if (!map) return;
  
          heatmap.clear();
          this.reposition();
  
          if (dataLen) {
  
              for (var i = 0; i < dataLen; i++) {
                  var dataVal = data[i],
                      latlng = L.latLng(dataVal),
                      point = map.latLngToContainerPoint(latlng);
  
                  heatmap.addPoint(
                      floor(point.x),
                      floor(point.y),
                      scaleFn(latlng),
                      dataVal[2]
                  );
              }
  
              heatmap.update();
  
              if (multiply) {
                  heatmap.multiply(multiply);
                  heatmap.update();
              }
  
          }
          heatmap.display();
      }
docs: draw function