v8/test/mjsunit/es6/proxies-has.js

// Copyright 2015 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.

var target = {
  "target_one": 1
};
target.__proto__ = {
  "target_two": 2
};
var handler = {
  has: function(target, name) {
    return name == "present";
  }
}

var proxy = new Proxy(target, handler);

// Test simple cases.
assertTrue("present" in proxy);
assertFalse("nonpresent" in proxy);

// Test interesting algorithm steps:

// Step 7: Fall through to target if trap is undefined.
handler.has = undefined;
assertTrue("target_one" in proxy);
assertTrue("target_two" in proxy);
assertFalse("in_your_dreams" in proxy);

// Step 8: Result is converted to boolean.
var result = 1;
handler.has = function(t, n) { return result; }
assertTrue("foo" in proxy);
result = {};
assertTrue("foo" in proxy);
result = undefined;
assertFalse("foo" in proxy);
result = "string";
assertTrue("foo" in proxy);

// Step 9b i. Trap result must confirm presence of non-configurable properties
// of the target.
Object.defineProperty(target, "nonconf", {value: 1, configurable: false});
result = false;
assertThrows("'nonconf' in proxy", TypeError);

// Step 9b iii. Trap result must confirm presence of all own properties of
// non-extensible targets.
Object.preventExtensions(target);
assertThrows("'nonconf' in proxy", TypeError);
assertThrows("'target_one' in proxy", TypeError);
assertFalse("target_two" in proxy);
assertFalse("in_your_dreams" in proxy);

// Regression test for crbug.com/570120 (stray JSObject::cast).
(function TestHasPropertyFastPath() {
  var proxy = new Proxy({}, {});
  var object = Object.create(proxy);
  object.hasOwnProperty(0);
})();