v8/test/mjsunit/compiler/object-create.js

// Copyright 2018 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

(function TestWithNullPrototype() {
  function f() { return Object.create(null); }
  %PrepareFunctionForOptimization(f);
  f();
  %OptimizeFunctionOnNextCall(f);
  assertEquals(undefined, f().foo);
})();

(function TestWithCustomPrototype() {
  const x = {foo: 42};  // This must be defined here for context specialization.
  function f() { return Object.create(x); }
  %PrepareFunctionForOptimization(f);
  f();
  %OptimizeFunctionOnNextCall(f);
  assertEquals(42, f().foo);
})();

(function TestWithObjectPrototype() {
  function f() { return Object.create(Object.prototype); }
  %PrepareFunctionForOptimization(f);
  f();
  %OptimizeFunctionOnNextCall(f);
  assertEquals("[object Object]", f().toString());
})();