Remove a couple calls to helpers.each (chartjs#6594)

src/core/core.controller.js

@@ -417,32 +417,35 @@ helpers.extend(Chart.prototype, /** @lends Chart */ {
 	buildOrUpdateControllers: function() {
 		var me = this;
 		var newControllers = [];
+		var datasets = me.data.datasets;
+		var i, ilen;
 
-		helpers.each(me.data.datasets, function(dataset, datasetIndex) {
-			var meta = me.getDatasetMeta(datasetIndex);
+		for (i = 0, ilen = datasets.length; i < ilen; i++) {
+			var dataset = datasets[i];
+			var meta = me.getDatasetMeta(i);
 			var type = dataset.type || me.config.type;
 
 			if (meta.type && meta.type !== type) {
-				me.destroyDatasetMeta(datasetIndex);
-				meta = me.getDatasetMeta(datasetIndex);
+				me.destroyDatasetMeta(i);
+				meta = me.getDatasetMeta(i);
 			}
 			meta.type = type;
 			meta.order = dataset.order || 0;
-			meta.index = datasetIndex;
+			meta.index = i;
 
 			if (meta.controller) {
-				meta.controller.updateIndex(datasetIndex);
+				meta.controller.updateIndex(i);
 				meta.controller.linkScales();
 			} else {
 				var ControllerClass = controllers[meta.type];
 				if (ControllerClass === undefined) {
 					throw new Error('"' + meta.type + '" is not a chart type.');
 				}
 
-				meta.controller = new ControllerClass(me, datasetIndex);
+				meta.controller = new ControllerClass(me, i);
 				newControllers.push(meta.controller);
 			}
-		}, me);
+		}
 
 		return newControllers;
 	},
@@ -468,6 +471,7 @@ helpers.extend(Chart.prototype, /** @lends Chart */ {
 
 	update: function(config) {
 		var me = this;
+		var i, ilen;
 
 		if (!config || typeof config !== 'object') {
 			// backwards compatibility
@@ -494,9 +498,9 @@ helpers.extend(Chart.prototype, /** @lends Chart */ {
 		var newControllers = me.buildOrUpdateControllers();
 
 		// Make sure all dataset controllers have correct meta data counts
-		helpers.each(me.data.datasets, function(dataset, datasetIndex) {
-			me.getDatasetMeta(datasetIndex).controller.buildOrUpdateElements();
-		}, me);
+		for (i = 0, ilen = me.data.datasets.length; i < ilen; i++) {
+			me.getDatasetMeta(i).controller.buildOrUpdateElements();
+		}
 
 		me.updateLayout();