Implement ES6 Array.of()

test/mjsunit/harmony/array-of.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Based on Mozilla Array.of() tests at http://dxr.mozilla.org/mozilla-central/source/js/src/jit-test/tests/collections
+
+// Flags: --harmony-arrays
+
+
+
+// Array.of makes real arrays.
+
+function check(a) {
+    assertEquals(Object.getPrototypeOf(a), Array.prototype);
+    assertEquals(Array.isArray(a), true);
+    a[9] = 9;
+    assertEquals(a.length, 10);
+}
+
+
+check(Array.of());
+check(Array.of(0));
+check(Array.of(0, 1, 2));
+var f = Array.of;
+check(f());
+
+
+// Array.of basics
+
+var a = Array.of();
+
+assertEquals(a.length, 0);
+a = Array.of(undefined, null, 3.14, []);
+assertEquals(a, [undefined, null, 3.14, []]);
+a = [];
+for (var i = 0; i < 1000; i++)
+    a[i] = i;
+assertEquals(Array.of.apply(null, a), a);
+
+
+// Array.of does not leave holes
+
+assertEquals(Array.of(undefined), [undefined]);
+assertEquals(Array.of(undefined, undefined), [undefined, undefined]);
+assertEquals(Array.of.apply(null, [,,undefined]), [undefined, undefined, undefined]);
+assertEquals(Array.of.apply(null, Array(4)), [undefined, undefined, undefined, undefined]);
+
+
+// Array.of can be transplanted to other classes.
+
+var hits = 0;
+function Bag() {
+    hits++;
+}
+Bag.of = Array.of;
+
+hits = 0;
+var actual = Bag.of("zero", "one");
+assertEquals(hits, 1);
+
+hits = 0;
+var expected = new Bag;
+expected[0] = "zero";
+expected[1] = "one";
+expected.length = 2;
+assertEquals(areSame(actual, expected), true);
+
+hits = 0;
+actual = Array.of.call(Bag, "zero", "one");
+assertEquals(hits, 1);
+assertEquals(areSame(actual, expected), true);
+
+function areSame(object, array) {
+    var result = object.length == array.length;
+    for (var i = 0; i < object.length; i++) {
+        result = result && object[i] == array[i];
+    }
+    return result;
+}
+
+
+// Array.of does not trigger prototype setters.
+// (It defines elements rather than assigning to them.)
+
+var status = "pass";
+Object.defineProperty(Array.prototype, "0", {set: function(v) {status = "FAIL 1"}});
+assertEquals(Array.of(1)[0], 1);
+assertEquals(status, "pass");
+
+Object.defineProperty(Bag.prototype, "0", {set: function(v) {status = "FAIL 2"}});
+assertEquals(Bag.of(1)[0], 1);
+assertEquals(status, "pass");
+
+
+// Array.of passes the number of arguments to the constructor it calls.
+
+var hits = 0;
+
+function Herd(n) {
+    assertEquals(arguments.length, 1);
+    assertEquals(n, 5);
+    hits++;
+}
+
+Herd.of = Array.of;
+Herd.of("sheep", "cattle", "elephants", "whales", "seals");
+assertEquals(hits, 1);
+
+
+// Array.of calls a "length" setter if one is present.
+
+var hits = 0;
+var lastObj = null, lastVal = undefined;
+function setter(v) {
+    hits++;
+    lastObj = this;
+    lastVal = v;
+}
+
+// when the setter is on the new object
+function Pack() {
+    Object.defineProperty(this, "length", {set: setter});
+}
+Pack.of = Array.of;
+var pack = Pack.of("wolves", "cards", "cigarettes", "lies");
+assertEquals(lastObj, pack);
+assertEquals(lastVal, 4);
+
+// when the setter is on the new object's prototype
+function Bevy() {}
+Object.defineProperty(Bevy.prototype, "length", {set: setter});
+Bevy.of = Array.of;
+var bevy = Bevy.of("quail");
+assertEquals(lastObj, bevy);
+assertEquals(lastVal, 1);
+
+
+// Array.of does a strict assignment to the new object's .length.
+// The assignment is strict even if the code we're calling from is not strict.
+
+function Empty() {}
+Empty.of = Array.of;
+Object.defineProperty(Empty.prototype, "length", {get: function() { return 0; }});
+
+var nothing = new Empty;
+nothing.length = 2;  // no exception; this is not a strict mode assignment
+
+assertThrows(function() { Empty.of(); }, TypeError);
+
+
+// Check superficial features of Array.of.
+
+var desc = Object.getOwnPropertyDescriptor(Array, "of");
+
+assertEquals(desc.configurable, true);
+assertEquals(desc.enumerable, false);
+assertEquals(desc.writable, true);
+assertEquals(Array.of.length, 0);
+assertThrows(function() { new Array.of() }, TypeError);  // not a constructor
+
+// When the this-value passed in is not a constructor, the result is an array.
+[undefined, null, false, "cow"].forEach(function(val) {
+    assertEquals(Array.isArray(Array.of(val)), true);
+});