Clone 3.5.1 from github

vendors/knockout/src/utils.domData.js

@@ -0,0 +1,74 @@
+
+ko.utils.domData = new (function () {
+    var uniqueId = 0;
+    var dataStoreKeyExpandoPropertyName = "__ko__" + (new Date).getTime();
+    var dataStore = {};
+
+    var getDataForNode, clear;
+    if (!ko.utils.ieVersion) {
+        // We considered using WeakMap, but it has a problem in IE 11 and Edge that prevents using
+        // it cross-window, so instead we just store the data directly on the node.
+        // See https://github.com/knockout/knockout/issues/2141
+        getDataForNode = function (node, createIfNotFound) {
+            var dataForNode = node[dataStoreKeyExpandoPropertyName];
+            if (!dataForNode && createIfNotFound) {
+                dataForNode = node[dataStoreKeyExpandoPropertyName] = {};
+            }
+            return dataForNode;
+        };
+        clear = function (node) {
+            if (node[dataStoreKeyExpandoPropertyName]) {
+                delete node[dataStoreKeyExpandoPropertyName];
+                return true; // Exposing "did clean" flag purely so specs can infer whether things have been cleaned up as intended
+            }
+            return false;
+        };
+    } else {
+        // Old IE versions have memory issues if you store objects on the node, so we use a
+        // separate data storage and link to it from the node using a string key.
+        getDataForNode = function (node, createIfNotFound) {
+            var dataStoreKey = node[dataStoreKeyExpandoPropertyName];
+            var hasExistingDataStore = dataStoreKey && (dataStoreKey !== "null") && dataStore[dataStoreKey];
+            if (!hasExistingDataStore) {
+                if (!createIfNotFound)
+                    return undefined;
+                dataStoreKey = node[dataStoreKeyExpandoPropertyName] = "ko" + uniqueId++;
+                dataStore[dataStoreKey] = {};
+            }
+            return dataStore[dataStoreKey];
+        };
+        clear = function (node) {
+            var dataStoreKey = node[dataStoreKeyExpandoPropertyName];
+            if (dataStoreKey) {
+                delete dataStore[dataStoreKey];
+                node[dataStoreKeyExpandoPropertyName] = null;
+                return true; // Exposing "did clean" flag purely so specs can infer whether things have been cleaned up as intended
+            }
+            return false;
+        };
+    }
+
+    return {
+        get: function (node, key) {
+            var dataForNode = getDataForNode(node, false);
+            return dataForNode && dataForNode[key];
+        },
+        set: function (node, key, value) {
+            // Make sure we don't actually create a new domData key if we are actually deleting a value
+            var dataForNode = getDataForNode(node, value !== undefined /* createIfNotFound */);
+            dataForNode && (dataForNode[key] = value);
+        },
+        getOrSet: function (node, key, value) {
+            var dataForNode = getDataForNode(node, true /* createIfNotFound */);
+            return dataForNode[key] || (dataForNode[key] = value);
+        },
+        clear: clear,
+
+        nextKey: function () {
+            return (uniqueId++) + dataStoreKeyExpandoPropertyName;
+        }
+    };
+})();
+
+ko.exportSymbol('utils.domData', ko.utils.domData);
+ko.exportSymbol('utils.domData.clear', ko.utils.domData.clear); // Exporting only so specs can clear up after themselves fully