More efficient array management in Polymer.DomApi.

src/lib/dom-api.html

@@ -356,7 +356,7 @@
         if (node.nodeType === Node.DOCUMENT_FRAGMENT_NODE) {
           // NOTE: the act of setting this info can affect patched nodes
           // getters; therefore capture childNodes before patching.
-          var c$ = Array.prototype.slice.call(node.childNodes);
+          var c$ = arrayCopyNodes(node.childNodes);
           for (var i=0, n; (i<c$.length) && (n=c$[i]); i++) {
             children.splice(index++, 0, n);
             n._lightParent = container;
@@ -585,7 +585,7 @@
         childNodes: {
           get: function() {
             var c$ = getLightChildren(this.node);
-            return Array.isArray(c$) ? c$ : Array.prototype.slice.call(c$);
+            return Array.isArray(c$) ? c$ : arrayCopyNodes(c$);
           },
           configurable: true
         },
@@ -722,7 +722,9 @@
               this._clear();
               var d = document.createElement('div');
               d.innerHTML = text;
-              var c$ = Array.prototype.slice.call(d.childNodes);
+              // here, appendChild may move nodes async so we cannot rely 
+              // on node position when copying
+              var c$ = arrayCopyNodes(d.childNodes);
               for (var i=0; i < c$.length; i++) {
                 this.appendChild(c$[i]);
               }
@@ -740,17 +742,22 @@
 
     } else {
 
-      var forwardMethods = ['cloneNode', 'appendChild', 'insertBefore', 
-      'removeChild', 'replaceChild'];
-
-      forwardMethods.forEach(function(name) {
+      function forwardMethods(m$) {
+        for (var i=0; i < m$.length; i++) {
+          fowardMethod(m$[i]);
+        }
+      } 
+      function forwardMethod(method) {
         DomApi.prototype[name] = function() {
           return this.node[name].apply(this.node, arguments);
         }
-      });
+      }
+
+      forwardMethods(['cloneNode', 'appendChild', 'insertBefore', 
+        'removeChild', 'replaceChild'])
 
       DomApi.prototype.querySelectorAll = function(selector) {
-        return Array.prototype.slice.call(this.node.querySelectorAll(selector));
+        return arrayCopyNodes(this.node.querySelectorAll(selector));
       };
 
       DomApi.prototype.getOwnerRoot = function() {
@@ -772,13 +779,13 @@
       DomApi.prototype.getDestinationInsertionPoints = function() {
         var n$ = this.node.getDestinationInsertionPoints && 
           this.node.getDestinationInsertionPoints();
-        return n$ ? Array.prototype.slice.call(n$) : [];
+        return n$ ? arrayCopy(n$) : [];
       };
 
       DomApi.prototype.getDistributedNodes = function() {
         var n$ = this.node.getDistributedNodes && 
           this.node.getDistributedNodes();
-        return n$ ? Array.prototype.slice.call(n$) : [];
+        return n$ ? arrayCopy(n$) : [];
       };
 
       DomApi.prototype._distributeParent = function() {};
@@ -796,14 +803,14 @@
 
         childNodes: {
           get: function() {
-            return Array.prototype.slice.call(this.node.childNodes);
+            return arrayCopyNodes(this.node.childNodes);
           },
           configurable: true
         },
 
         children: {
           get: function() {
-            return Array.prototype.slice.call(this.node.children);
+            return arrayCopyNodes(this.node.children);
           },
           configurable: true
         },
@@ -831,18 +838,22 @@
 
       });
 
-      var forwardProperties = ['parentNode', 'firstChild', 'lastChild', 
-      'nextSibling', 'previousSibling', 'firstElementChild', 'lastElementChild',
-      'nextElementSibling', 'previousElementSibling'];
-
-      forwardProperties.forEach(function(name) {
+      function forwardProperties(f$) {
+        for (var i=0; i < f$.length; i++) {
+          forwardProperty(f$[i]);
+        }
+      }
+      function forwardProperty(name) {
         Object.defineProperty(DomApi.prototype, name, {
           get: function() {
             return this.node[name];
           },
           configurable: true
         });
-      });
+      }
+      forwardProperties(['parentNode', 'firstChild', 'lastChild', 
+      'nextSibling', 'previousSibling', 'firstElementChild', 'lastElementChild',
+      'nextElementSibling', 'previousElementSibling']);
 
     }
 
@@ -878,7 +889,7 @@
 
     function getComposedChildren(node) {
       if (!node._composedChildren) {
-        node._composedChildren = Array.prototype.slice.call(node.childNodes);
+        node._composedChildren = arrayCopyNodes(node.childNodes);
       }
       return node._composedChildren;
     }
@@ -939,6 +950,23 @@
       }
     }
 
+    // sad but faster than slice...
+    function arrayCopyNodes(childNodes) {
+      var copy=[], i=0;
+      for (var n=childNodes.firstChild; n; n=n.nextSibling) {
+        copy[i++] = n;
+      }
+      return copy;
+    }
+
+    function arrayCopy(a$) {
+      var copy = new Array(a$.length);
+      for (var i=0; i < a$.length; i++) {
+        copy[i] = a$[i];
+      }
+      return copy;
+    }
+
     function hasInsertionPoint(root) {
       return Boolean(root && root._insertionPoints.length);
     }