updated to use own valueOf when available

Author: HeberLZ

src/Angular.js

@@ -126,7 +126,6 @@ var VALIDITY_STATE_PROPERTY = 'validity';
  */
 var lowercase = function(string){return isString(string) ? string.toLowerCase() : string;};
 var hasOwnProperty = Object.prototype.hasOwnProperty;
-var valueOfObject = Object.prototype.valueOf;
 
 /**
  * @ngdoc function

src/ng/parse.js

@@ -946,6 +946,13 @@ function getterFn(path, options, fullExp) {
   return fn;
 }
 
+function valueOfAgnostic(value){
+  if(typeof value.valueOf !== 'function'){
+    return Object.prototype.valueOf.call(value);
+  }
+  return value.valueOf();
+}
+
 ///////////////////////////////////
 
 /**
@@ -1092,7 +1099,7 @@ function $ParseProvider() {
         // attempt to convert the value to a primitive type
         // TODO(docs): add a note to docs that by implementing valueOf even objects and arrays can
         //             be cheaply dirty-checked
-        newValue = valueOfObject.call(newValue);
+        newValue = valueOfAgnostic(newValue);
 
         if (typeof newValue === 'object') {
           // objects/arrays are not supported - deep-watching them would be too expensive
@@ -1119,7 +1126,7 @@ function $ParseProvider() {
           var newInputValue = inputExpressions(scope);
           if (!expressionInputDirtyCheck(newInputValue, oldInputValue)) {
             lastResult = parsedExpression(scope);
-            oldInputValue = newInputValue && valueOfObject.call(newInputValue);
+            oldInputValue = newInputValue && valueOfAgnostic(newInputValue);
           }
           return lastResult;
         }, listener, objectEquality);
@@ -1136,7 +1143,7 @@ function $ParseProvider() {
         for (var i = 0, ii = inputExpressions.length; i < ii; i++) {
           var newInputValue = inputExpressions[i](scope);
           if (changed || (changed = !expressionInputDirtyCheck(newInputValue, oldInputValueOfValues[i]))) {
-            oldInputValueOfValues[i] = newInputValue && valueOfObject.call(newInputValue);
+            oldInputValueOfValues[i] = newInputValue && valueOfAgnostic(newInputValue);
           }
         }