proxy enum/ownKeys test from guide

ecmascript-testcases/test-dev-proxy-enum-ownkeys-guide.js

@@ -0,0 +1,42 @@
+/*
+ *  Proxy enum/ownKeys example in guide.
+ */
+
+/*===
+foo
+bar
+foo,bar
+foo,bar
+===*/
+
+var target = {
+    foo: 1,
+    bar: 2,
+    _quux: 3,
+    _baz: 4
+};
+
+var proxy = new Proxy(target, {
+    enumerate: function (targ) {
+        // this binding: handler table
+        // targ: underlying plain object (= target, above)
+
+        return Object.getOwnPropertyNames(targ)
+                     .filter(function (v) { return v[0] !== '_'; });
+    },
+
+    ownKeys: function (targ) {
+        return Object.getOwnPropertyNames(targ)
+                     .filter(function (v) { return v[0] !== '_'; });
+    }
+});
+
+function test() {
+    for (var k in proxy) {
+        print(k);  // prints 'foo' and 'bar'
+    }
+}
+test();
+
+print(Object.keys(proxy));                 // prints 'foo,bar'
+print(Object.getOwnPropertyNames(proxy));  // prints 'foo,bar'