LibJS: Implement most of the Reflect object

Libraries/LibJS/Tests/Reflect.set.js

@@ -0,0 +1,54 @@
+load("test-common.js");
+
+try {
+    assert(Reflect.set.length === 3);
+
+    [null, undefined, "foo", 123, NaN, Infinity].forEach(value => {
+        assertThrowsError(() => {
+            Reflect.set(value);
+        }, {
+            error: TypeError,
+            message: "First argument of Reflect.set() must be an object"
+        });
+    });
+
+    assert(Reflect.set({}) === true);
+    assert(Reflect.set({}, "foo") === true);
+    assert(Reflect.set({}, "foo", "bar") === true);
+
+    var o = {};
+    assert(o.foo === undefined);
+    assert(Reflect.set(o, "foo", 1) === true);
+    assert(o.foo === 1);
+    assert(Reflect.set(o, "foo", 2) === true);
+    assert(o.foo === 2);
+
+    Object.defineProperty(o, "bar", { value: 2, configurable: true, writable: false });
+    assert(Reflect.set(o, "bar") === false);
+    assert(o.bar === 2);
+
+    Object.defineProperty(o, "baz", { value: 3, configurable: false, writable: true });
+    assert(Reflect.set(o, "baz") === true);
+    assert(o.baz === undefined);
+
+    var a = [];
+    assert(a.length === 0);
+    assert(Reflect.set(a, "0") === true);
+    assert(a.length === 1);
+    assert(a[0] === undefined);
+    assert(Reflect.set(a, 1, "foo") === true);
+    assert(a.length === 2);
+    assert(a[0] === undefined);
+    assert(a[1] === "foo");
+    assert(Reflect.set(a, 4, "bar") === true);
+    assert(a.length === 5);
+    assert(a[0] === undefined);
+    assert(a[1] === "foo");
+    assert(a[2] === undefined);
+    assert(a[3] === undefined);
+    assert(a[4] === "bar");
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}