JezK
Edit File: object-prevent-extensions.js
// Copyright 2010 the V8 project authors. All rights reserved. // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions are // met: // // * Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // * Redistributions in binary form must reproduce the above // copyright notice, this list of conditions and the following // disclaimer in the documentation and/or other materials provided // with the distribution. // * Neither the name of Google Inc. nor the names of its // contributors may be used to endorse or promote products derived // from this software without specific prior written permission. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. // Tests the Object.preventExtensions method - ES 15.2.3.10 var obj1 = {}; // Extensible defaults to true. assertTrue(Object.isExtensible(obj1)); Object.preventExtensions(obj1); // Make sure the is_extensible flag is set. assertFalse(Object.isExtensible(obj1)); obj1.x = 42; assertEquals(undefined, obj1.x); // Try adding a new element. obj1[1] = 42; assertEquals(undefined, obj1[1]); // Try when the object has an existing property. var obj2 = {}; assertTrue(Object.isExtensible(obj2)); obj2.x = 42; assertEquals(42, obj2.x); assertTrue(Object.isExtensible(obj2)); Object.preventExtensions(obj2); assertEquals(42, obj2.x); obj2.y = 42; // obj2.y should still be undefined. assertEquals(undefined, obj2.y); // Make sure we can still write values to obj.x. obj2.x = 43; assertEquals(43, obj2.x) obj2.y = new function() { return 42; }; // obj2.y should still be undefined. assertEquals(undefined, obj2.y); assertEquals(43, obj2.x) try { Object.defineProperty(obj2, "y", {value: 42}); } catch (e) { assertTrue(/object is not extensible/.test(e)); } // obj2.y should still be undefined. assertEquals(undefined, obj2.y); assertEquals(43, obj2.x); obj2[1] = 42; assertEquals(undefined, obj2[1]); var arr = new Array(); arr[1] = 10; Object.preventExtensions(arr); arr[2] = 42; assertEquals(10, arr[1]); // We should still be able to change exiting elements. arr[1]= 42; assertEquals(42, arr[1]); // Test the the extensible flag is not inherited. var parent = {}; parent.x = 42; Object.preventExtensions(parent); var child = Object.create(parent); // We should be able to add new properties to the child object. child.y = 42; // This should have no influence on the parent class. parent.y = 29; // Test that attributes on functions are also handled correctly. function foo() { return 42; } Object.preventExtensions(foo); foo.x = 29; assertEquals(undefined, foo.x); // when Object.isExtensible(o) === false // assignment should return right hand side value var o = Object.preventExtensions({}); var v = o.v = 50; assertEquals(undefined, o.v); assertEquals(50, v); // test same behavior as above, but for integer properties var n = o[0] = 100; assertEquals(undefined, o[0]); assertEquals(100, n);