perf(ngRepeat): simplify code and remove duplicate array.length access

IgorMinar · IgorMinar · commit 08eb05583bf3 · 2014-08-18T21:20:10.000-07:00
minimal perf gain (~2ms)
diff --git a/src/ng/directive/ngRepeat.js b/src/ng/directive/ngRepeat.js
@@ -310,13 +310,13 @@ var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
               // Same as lastBlockMap but it has the current state. It will become the
               // lastBlockMap on the next iteration.
               nextBlockMap = createMap(),
-              arrayLength,
+              collectionLength,
               key, value, // key/value of iteration
               trackById,
               trackByIdFn,
               collectionKeys,
               block,       // last object information {scope, element, id}
-              nextBlockOrder = [],
+              nextBlockOrder,
               elementsToRemove;
 
           if (aliasAs) {
@@ -338,11 +338,11 @@ var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
             collectionKeys.sort();
           }
 
-          arrayLength = collectionKeys.length;
+          collectionLength = collectionKeys.length;
+          nextBlockOrder = new Array(collectionLength);
 
           // locate existing items
-          length = nextBlockOrder.length = collectionKeys.length;
-          for (index = 0; index < length; index++) {
+          for (index = 0; index < collectionLength; index++) {
             key = (collection === collectionKeys) ? index : collectionKeys[index];
             value = collection[key];
             trackById = trackByIdFn(key, value, index);
@@ -382,7 +382,7 @@ var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
           }
 
           // we are not using forEach for perf reasons (trying to avoid #call)
-          for (index = 0, length = collectionKeys.length; index < length; index++) {
+          for (index = 0; index < collectionLength; index++) {
             key = (collection === collectionKeys) ? index : collectionKeys[index];
             value = collection[key];
             block = nextBlockOrder[index];
@@ -401,7 +401,7 @@ var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
                 $animate.move(getBlockNodes(block.clone), null, jqLite(previousNode));
               }
               previousNode = getBlockEnd(block);
-              updateScope(block.scope, index, valueIdentifier, value, keyIdentifier, key, arrayLength);
+              updateScope(block.scope, index, valueIdentifier, value, keyIdentifier, key, collectionLength);
             } else {
               // new item which we don't know about
               $transclude(function ngRepeatTransclude(clone, scope) {
@@ -415,7 +415,7 @@ var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
                 // by a directive with templateUrl when its template arrives.
                 block.clone = clone;
                 nextBlockMap[block.id] = block;
-                updateScope(block.scope, index, valueIdentifier, value, keyIdentifier, key, arrayLength);
+                updateScope(block.scope, index, valueIdentifier, value, keyIdentifier, key, collectionLength);
               });
             }
           }
