v8/test/mjsunit/object-keys.js

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// Copyright 2017 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.
// Flags: --allow-natives-syntax
// Ensure that mutation of the Object.keys result doesn't affect the
// enumeration cache for fast-mode objects.
(function() {
const a = {x:1, y:2};
let k = Object.keys(a);
%HeapObjectVerify(k);
assertEquals(2, k.length);
assertEquals("x", k[0]);
assertEquals("y", k[1]);
k[0] = "y";
k[1] = "x";
k = Object.keys(a);
assertEquals(2, k.length);
assertEquals("x", k[0]);
assertEquals("y", k[1]);
})();
// Ensure that the copy-on-write keys are handled properly, even in
// the presence of Symbols.
(function() {
const s = Symbol();
const a = {[s]: 1};
let k = Object.keys(a);
%HeapObjectVerify(k);
assertEquals(0, k.length);
k.shift();
assertEquals(0, k.length);
})();