Add the elementData util library (still not in stable, though).

js/util/elementData.js

@@ -0,0 +1,39 @@
+define(function() {
+  
+  /*
+  
+  Storing JS data on HTML elements has, in the past, been a likely source of
+  memory leaks one way or the other. In this module, we create a set of
+  matching WeakMaps for connecting data to DOM and vice versa. The dom2 module
+  uses this to emulate jQuery's data() method, and other modules can import this
+  to ask for an element given a JS object (such as a tab instance).
+  
+  */
+  
+  var elements = new WeakMap();
+  var objects = new WeakMap();
+  
+  return {
+    get: function(key) {
+      var map = key instanceof HTMLElement ? elements : objects;
+      return map.get(key);
+    },
+    set: function(key, value) {
+      var isDom = key instanceof HTMLElement;
+      var forward = isDom ? elements : objects;
+      var reverse = isDom ? objects : elements;
+      forward.set(key, value);
+      reverse.set(value, key);
+    },
+    "delete": function(key) {
+      var isDom = key instanceof HTMLElement;
+      var forward = isDom ? elements : objects;
+      var reverse = isDom ? objects : elements;
+      var data = forward.get(key);
+      forward.delete(key);
+      reverse.delete(data);
+    }
+  }
+  
+  
+});