michael@0: // Basic for-of test with Proxy.
michael@0: 
michael@0: function iterableProxy(arr) {
michael@0:     return Proxy.create({
michael@0:         getPropertyDescriptor: function (name) {
michael@0:             for (var obj = arr; obj; obj = Object.getPrototypeOf(obj)) {
michael@0:                 var desc = Object.getOwnPropertyDescriptor(obj, name);
michael@0:                 if (desc)
michael@0:                     return desc;
michael@0:             }
michael@0:             return undefined;
michael@0:         }
michael@0:     });
michael@0: }
michael@0: 
michael@0: var s = '';
michael@0: var arr = ['a', 'b', 'c', 'd'];
michael@0: var p = iterableProxy(arr);
michael@0: 
michael@0: // Test the same proxy twice. Each time through the loop, the proxy handler's
michael@0: // getPropertyDescriptor method will be called 10 times (once for 'iterator',
michael@0: // five times for 'length', and once for each of the four elements).
michael@0: for (var i = 0; i < 2; i++) {
michael@0:     var j = 0;
michael@0:     for (var x of p)
michael@0:         assertEq(x, arr[j++]);
michael@0:     assertEq(j, arr.length);
michael@0: }