// 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.seal and Object.isSealed methods - ES 19.1.2.17 and // ES 19.1.2.13 // Flags: --allow-natives-syntax --opt --noalways-opt // Test that we return obj if non-object is passed as argument var non_objects = new Array(undefined, null, 1, -1, 0, 42.43, Symbol("test")); for (var key in non_objects) { assertSame(non_objects[key], Object.seal(non_objects[key])); } // Test that isFrozen always returns true for non-objects for (var key in non_objects) { assertTrue(Object.isSealed(non_objects[key])); } // Test normal data properties. var obj = { x: 42, z: 'foobar' }; var desc = Object.getOwnPropertyDescriptor(obj, 'x'); assertTrue(desc.writable); assertTrue(desc.configurable); assertEquals(42, desc.value); desc = Object.getOwnPropertyDescriptor(obj, 'z'); assertTrue(desc.writable); assertTrue(desc.configurable); assertEquals('foobar', desc.value); assertTrue(Object.isExtensible(obj)); assertFalse(Object.isSealed(obj)); Object.seal(obj); // Make sure we are no longer extensible. assertFalse(Object.isExtensible(obj)); assertTrue(Object.isSealed(obj)); // We should not be frozen, since we are still able to // update values. assertFalse(Object.isFrozen(obj)); // We should not allow new properties to be added. obj.foo = 42; assertEquals(obj.foo, undefined); desc = Object.getOwnPropertyDescriptor(obj, 'x'); assertTrue(desc.writable); assertFalse(desc.configurable); assertEquals(42, desc.value); desc = Object.getOwnPropertyDescriptor(obj, 'z'); assertTrue(desc.writable); assertFalse(desc.configurable); assertEquals("foobar", desc.value); // Since writable is not affected by seal we should still be able to // update the values. obj.x = "43"; assertEquals("43", obj.x); // Test on accessors. var obj2 = {}; function get() { return 43; }; function set() {}; Object.defineProperty(obj2, 'x', { get: get, set: set, configurable: true }); desc = Object.getOwnPropertyDescriptor(obj2, 'x'); assertTrue(desc.configurable); assertEquals(undefined, desc.value); assertEquals(set, desc.set); assertEquals(get, desc.get); assertTrue(Object.isExtensible(obj2)); assertFalse(Object.isSealed(obj2)); Object.seal(obj2); // Since this is an accessor property the object is now effectively both // sealed and frozen (accessors has no writable attribute). assertTrue(Object.isFrozen(obj2)); assertFalse(Object.isExtensible(obj2)); assertTrue(Object.isSealed(obj2)); desc = Object.getOwnPropertyDescriptor(obj2, 'x'); assertFalse(desc.configurable); assertEquals(undefined, desc.value); assertEquals(set, desc.set); assertEquals(get, desc.get); obj2.foo = 42; assertEquals(obj2.foo, undefined); // Test seal on arrays. var arr = new Array(42,43); desc = Object.getOwnPropertyDescriptor(arr, '0'); assertTrue(desc.configurable); assertTrue(desc.writable); assertEquals(42, desc.value); desc = Object.getOwnPropertyDescriptor(arr, '1'); assertTrue(desc.configurable); assertTrue(desc.writable); assertEquals(43, desc.value); assertTrue(Object.isExtensible(arr)); assertFalse(Object.isSealed(arr)); Object.seal(arr); assertTrue(Object.isSealed(arr)); assertFalse(Object.isExtensible(arr)); // Since the values in the array is still writable this object // is not frozen. assertFalse(Object.isFrozen(arr)); desc = Object.getOwnPropertyDescriptor(arr, '0'); assertFalse(desc.configurable); assertTrue(desc.writable); assertEquals(42, desc.value); desc = Object.getOwnPropertyDescriptor(arr, '1'); assertFalse(desc.configurable); assertTrue(desc.writable); assertEquals(43, desc.value); arr[0] = 'foo'; // We should be able to overwrite the existing value. assertEquals('foo', arr[0]); // Test that isSealed returns the correct value even if configurable // has been set to false on all properties manually and the extensible // flag has also been set to false manually. var obj3 = { x: 42, y: 'foo' }; assertFalse(Object.isFrozen(obj3)); Object.defineProperty(obj3, 'x', {configurable: false, writable: true}); Object.defineProperty(obj3, 'y', {configurable: false, writable: false}); Object.preventExtensions(obj3); assertTrue(Object.isSealed(obj3)); // Make sure that an object that has a configurable property // is not classified as sealed. var obj4 = {}; Object.defineProperty(obj4, 'x', {configurable: true, writable: false}); Object.defineProperty(obj4, 'y', {configurable: false, writable: false}); Object.preventExtensions(obj4); assertFalse(Object.isSealed(obj4)); // Make sure that Object.seal returns the sealed object. var obj4 = {}; assertTrue(obj4 === Object.seal(obj4)); // // Test that built-in array functions can't modify a sealed array. // obj = [1, 2, 3]; var objControl = [4, 5, 6]; // Allow these functions to set up monomorphic calls, using custom built-ins. var push_call = function(a) { a.push(10); return a; } var pop_call = function(a) { return a.pop(); } for (var i = 0; i < 3; i++) { push_call(obj); pop_call(obj); } Object.seal(obj); assertThrows(function() { push_call(obj); }, TypeError); assertThrows(function() { pop_call(obj); }, TypeError); // But the control object is fine at these sites. assertDoesNotThrow(function() { push_call(objControl); }); assertDoesNotThrow(function() { pop_call(objControl); }); assertDoesNotThrow(function() { obj.push(); }); assertThrows(function() { obj.push(3); }, TypeError); assertThrows(function() { obj.pop(); }, TypeError); assertThrows(function() { obj.shift(3); }, TypeError); assertDoesNotThrow(function() { obj.unshift(); }); assertThrows(function() { obj.unshift(1); }, TypeError); assertThrows(function() { obj.splice(0, 0, 100, 101, 102); }, TypeError); assertDoesNotThrow(function() { obj.splice(0,0); }); assertDoesNotThrow(function() { objControl.push(3); }); assertDoesNotThrow(function() { objControl.pop(); }); assertDoesNotThrow(function() { objControl.shift(3); }); assertDoesNotThrow(function() { objControl.unshift(); }); assertDoesNotThrow(function() { objControl.splice(0, 0, 100, 101, 102); }); // Verify that crankshaft still does the right thing. obj = [1, 2, 3]; push_call = function(a) { a.push(1000); return a; }; %PrepareFunctionForOptimization(push_call); // Include a call site that doesn't have a custom built-in. var shift_call = function(a) { a.shift(1000); return a; }; %PrepareFunctionForOptimization(shift_call); for (var i = 0; i < 3; i++) { push_call(obj); shift_call(obj); } %OptimizeFunctionOnNextCall(push_call); %OptimizeFunctionOnNextCall(shift_call); push_call(obj); shift_call(obj); assertOptimized(push_call); assertOptimized(shift_call); Object.seal(obj); assertThrows(function() { push_call(obj); }, TypeError); assertThrows(function() { shift_call(obj); }, TypeError); assertUnoptimized(push_call); assertUnoptimized(shift_call); assertDoesNotThrow(function() { push_call(objControl); }); assertDoesNotThrow(function() { shift_call(objControl); }); // Verify special behavior of splice on sealed objects. obj = [1,2,3]; Object.seal(obj); assertDoesNotThrow(function() { obj.splice(0,1,100); }); assertEquals(100, obj[0]); assertDoesNotThrow(function() { obj.splice(0,2,1,2); }); assertDoesNotThrow(function() { obj.splice(1,2,1,2); }); // Count of items to delete is clamped by length. assertDoesNotThrow(function() { obj.splice(1,2000,1,2); }); assertThrows(function() { obj.splice(0,0,1); }, TypeError); assertThrows(function() { obj.splice(1,2000,1,2,3); }, TypeError); // Test that the enumerable attribute is unperturbed by sealing. obj = { x: 42, y: 'foo' }; Object.defineProperty(obj, 'y', {enumerable: false}); Object.seal(obj); assertTrue(Object.isSealed(obj)); assertFalse(Object.isFrozen(obj)); desc = Object.getOwnPropertyDescriptor(obj, 'x'); assertTrue(desc.enumerable); desc = Object.getOwnPropertyDescriptor(obj, 'y'); assertFalse(desc.enumerable); // Fast properties should remain fast obj = { x: 42, y: 'foo' }; assertTrue(%HasFastProperties(obj)); Object.seal(obj); assertTrue(Object.isSealed(obj)); assertFalse(Object.isFrozen(obj)); assertTrue(%HasFastProperties(obj)); // Sealed objects should share maps where possible obj = { prop1: 1, prop2: 2 }; obj2 = { prop1: 3, prop2: 4 }; assertTrue(%HaveSameMap(obj, obj2)); Object.seal(obj); Object.seal(obj2); assertTrue(Object.isSealed(obj)); assertTrue(Object.isSealed(obj2)); assertFalse(Object.isFrozen(obj)); assertFalse(Object.isFrozen(obj2)); assertTrue(%HaveSameMap(obj, obj2)); // Sealed objects should share maps even when they have elements obj = { prop1: 1, prop2: 2, 75: 'foo' }; obj2 = { prop1: 3, prop2: 4, 150: 'bar' }; assertTrue(%HaveSameMap(obj, obj2)); Object.seal(obj); Object.seal(obj2); assertTrue(Object.isSealed(obj)); assertTrue(Object.isSealed(obj2)); assertFalse(Object.isFrozen(obj)); assertFalse(Object.isFrozen(obj)); assertTrue(%HaveSameMap(obj, obj2)); // Setting elements after sealing should not be allowed obj = { prop: 'thing' }; Object.seal(obj); assertTrue(Object.isSealed(obj)); assertFalse(Object.isFrozen(obj)); obj[0] = 'hello'; assertFalse(obj.hasOwnProperty(0)); // Sealing an object in dictionary mode should work // Also testing that getter/setter properties work after sealing obj = { }; for (var i = 0; i < 100; ++i) { obj['x' + i] = i; } var accessorDidRun = false; Object.defineProperty(obj, 'accessor', { get: function() { return 42 }, set: function() { accessorDidRun = true }, configurable: true, enumerable: true }); assertFalse(%HasFastProperties(obj)); Object.seal(obj); assertFalse(%HasFastProperties(obj)); assertTrue(Object.isSealed(obj)); assertFalse(Object.isFrozen(obj)); assertFalse(Object.isExtensible(obj)); for (var i = 0; i < 100; ++i) { desc = Object.getOwnPropertyDescriptor(obj, 'x' + i); assertFalse(desc.configurable); } assertEquals(42, obj.accessor); assertFalse(accessorDidRun); obj.accessor = 'ignored value'; assertTrue(accessorDidRun); // Sealing arguments should work var func = function(arg) { Object.seal(arguments); assertTrue(Object.isSealed(arguments)); }; func('hello', 'world'); func('goodbye', 'world'); // Sealing sparse arrays var sparseArr = [0, 1]; sparseArr[10000] = 10000; Object.seal(sparseArr); assertTrue(Object.isSealed(sparseArr)); // Accessors on fast object should behavior properly after sealing obj = {}; Object.defineProperty(obj, 'accessor', { get: function() { return 42 }, set: function() { accessorDidRun = true }, configurable: true, enumerable: true }); assertTrue(%HasFastProperties(obj)); Object.seal(obj); assertTrue(Object.isSealed(obj)); assertTrue(%HasFastProperties(obj)); assertEquals(42, obj.accessor); accessorDidRun = false; obj.accessor = 'ignored value'; assertTrue(accessorDidRun); // Test for regression in mixed accessor/data property objects. // The strict function is one such object. assertTrue(Object.isSealed(Object.seal(function(){"use strict";}))); // Also test a simpler case obj = {}; Object.defineProperty(obj, 'accessor2', { get: function() { return 42 }, set: function() { accessorDidRun = true }, configurable: true, enumerable: true }); obj.data = 'foo'; assertTrue(%HasFastProperties(obj)); Object.seal(obj); assertTrue(%HasFastProperties(obj)); assertTrue(Object.isSealed(obj)); function Sealed() {} Object.seal(Sealed); assertDoesNotThrow(function() { return new Sealed(); }); Sealed.prototype.prototypeExists = true; assertTrue((new Sealed()).prototypeExists); obj = new Int32Array(10); Object.seal(obj); assertTrue(Object.isSealed(obj)); // Test packed element array built-in functions with seal. function testPackedSealedArray1(obj) { assertTrue(Object.isSealed(obj)); assertFalse(Object.isFrozen(obj)); assertTrue(Array.isArray(obj)); // Verify that the length can't be written by builtins. assertThrows(function() { obj.pop(); }, TypeError); assertThrows(function() { obj.push(1); }, TypeError); assertThrows(function() { obj.shift(); }, TypeError); assertThrows(function() { obj.unshift(1); }, TypeError); assertThrows(function() { obj.splice(0); }, TypeError); assertDoesNotThrow(function() { obj.splice(0, 0); }); // Verify search, filter, iterator obj = new Array(undefined, null, 1, -1, 'a', Symbol("test")); assertTrue(%HasPackedElements(obj)); Object.seal(obj); assertTrue(Object.isSealed(obj)); assertFalse(Object.isFrozen(obj)); assertTrue(Array.isArray(obj)); assertEquals(obj.lastIndexOf(1), 2); assertEquals(obj.indexOf('a'), 4); assertEquals(obj.indexOf(undefined), 0); assertFalse(obj.includes(Symbol("test"))); assertTrue(obj.includes(undefined)); assertFalse(obj.includes(NaN)); assertTrue(obj.includes()); assertEquals(obj.find(x => x==0), undefined); assertEquals(obj.findIndex(x => x=='a'), 4); assertTrue(obj.some(x => typeof x == 'symbol')); assertFalse(obj.every(x => x == -1)); var filteredArray = obj.filter(e => typeof e == "symbol"); assertEquals(filteredArray.length, 1); assertEquals(obj.map(x => x), obj); var countPositiveNumber = 0; obj.forEach(function(item, index) { if (item === 1) { countPositiveNumber++; assertEquals(index, 2); } }); assertEquals(countPositiveNumber, 1); assertEquals(obj.length, obj.concat([]).length); var iterator = obj.values(); assertEquals(iterator.next().value, undefined); assertEquals(iterator.next().value, null); var iterator = obj.keys(); assertEquals(iterator.next().value, 0); assertEquals(iterator.next().value, 1); var iterator = obj.entries(); assertEquals(iterator.next().value, [0, undefined]); assertEquals(iterator.next().value, [1, null]); // Verify that the value can be written var length = obj.length; for (var i = 0; i < length-1; i++) { obj[i] = 'new'; assertEquals(obj[i], 'new'); } }; obj = new Array(undefined, null, 1, -1, 'a', Symbol("test")); assertTrue(%HasPackedElements(obj)); Object.seal(obj); testPackedSealedArray1(obj); // Verify after transition from preventExtensions obj = new Array(undefined, null, 1, -1, 'a', Symbol("test")); assertTrue(%HasPackedElements(obj)); Object.preventExtensions(obj); Object.seal(obj); testPackedSealedArray1(obj); // Verify flat, map, slice, flatMap, join, reduce, reduceRight for sealed packed array function testPackedSealedArray2(arr) { assertTrue(Object.isSealed(arr)); assertFalse(Object.isFrozen(arr)); assertEquals(arr.map(x => [x]), [['a'], ['b'], ['c']]); assertEquals(arr.flatMap(x => [x]), arr); assertEquals(arr.flat(), arr); assertEquals(arr.join('-'), "a-b-c"); const reducer = (accumulator, currentValue) => accumulator + currentValue; assertEquals(arr.reduce(reducer), "abc"); assertEquals(arr.reduceRight(reducer), "cba"); assertEquals(arr.slice(0, 1), ['a']); // Verify change content of sealed packed array arr.sort(); assertEquals(arr.join(''), "abc"); arr.reverse(); assertEquals(arr.join(''), "cba"); arr.copyWithin(0, 1, 2); assertEquals(arr.join(''),"bba"); arr.fill('d'); assertEquals(arr.join(''), "ddd"); } var arr1 = new Array('a', 'b', 'c'); assertTrue(%HasPackedElements(arr1)); Object.seal(arr1); testPackedSealedArray2(arr1); var arr2 = new Array('a', 'b', 'c'); assertTrue(%HasPackedElements(arr2)); Object.preventExtensions(arr2); Object.seal(arr2); testPackedSealedArray2(arr2); // Test regression with Object.defineProperty var obj = []; obj.propertyA = 42; obj[0] = true; Object.seal(obj); assertDoesNotThrow(function() { Object.defineProperty(obj, 'propertyA', { value: obj, }); }); assertEquals(obj, obj.propertyA); assertDoesNotThrow(function() { Object.defineProperty(obj, 'propertyA', { value: obj, writable: false, }); }); obj.propertyA = 42; assertEquals(obj.propertyA, 42); assertThrows(function() { Object.defineProperty(obj, 'abc', { value: obj, }); }, TypeError); // Regression test with simple array var arr = ['a']; Object.seal(arr); arr[0] = 'b'; assertEquals(arr[0], 'b'); // Test regression Array.concat with double var arr = ['a']; Object.seal(arr); arr = arr.concat(0.5); assertEquals(arr, ['a', 0.5]); Object.seal(arr); arr = arr.concat([1.5, 'b']); assertEquals(arr, ['a', 0.5, 1.5, 'b']); // Regression test with change length var arr = ['a', 'b']; Object.seal(arr); assertEquals(arr.length, 2); arr.length = 3; assertEquals(arr.length, 3); arr[2] = 'c'; assertEquals(arr[2], undefined); arr.length = 1; assertEquals(arr.length, 2); // Start testing for holey element array // Test holey element array built-in functions with seal. function testHoleySealedArray1(obj) { assertTrue(Object.isSealed(obj)); assertFalse(Object.isFrozen(obj)); assertTrue(Array.isArray(obj)); // Verify that the length can't be written by builtins. assertThrows(function() { obj.pop(); }, TypeError); assertThrows(function() { obj.push(1); }, TypeError); assertThrows(function() { obj.shift(); }, TypeError); assertThrows(function() { obj.unshift(1); }, TypeError); assertThrows(function() { obj.splice(0); }, TypeError); assertDoesNotThrow(function() { obj.splice(0, 0); }); // Verify search, filter, iterator obj = [undefined, null, 1, , -1, 'a', Symbol("test")]; assertTrue(%HasHoleyElements(obj)); Object.seal(obj); assertTrue(Object.isSealed(obj)); assertFalse(Object.isFrozen(obj)); assertTrue(Array.isArray(obj)); assertEquals(obj.lastIndexOf(1), 2); assertEquals(obj.indexOf('a'), 5); assertEquals(obj.indexOf(undefined), 0); assertFalse(obj.includes(Symbol("test"))); assertTrue(obj.includes(undefined)); assertFalse(obj.includes(NaN)); assertTrue(obj.includes()); assertEquals(obj.find(x => x==0), undefined); assertEquals(obj.findIndex(x => x=='a'), 5); assertTrue(obj.some(x => typeof x == 'symbol')); assertFalse(obj.every(x => x == -1)); var filteredArray = obj.filter(e => typeof e == "symbol"); assertEquals(filteredArray.length, 1); assertEquals(obj.map(x => x), obj); var countPositiveNumber = 0; obj.forEach(function(item, index) { if (item === 1) { countPositiveNumber++; assertEquals(index, 2); } }); assertEquals(countPositiveNumber, 1); assertEquals(obj.length, obj.concat([]).length); var iterator = obj.values(); assertEquals(iterator.next().value, undefined); assertEquals(iterator.next().value, null); var iterator = obj.keys(); assertEquals(iterator.next().value, 0); assertEquals(iterator.next().value, 1); var iterator = obj.entries(); assertEquals(iterator.next().value, [0, undefined]); assertEquals(iterator.next().value, [1, null]); // Verify that the value can be written var length = obj.length; for (var i = 0; i < length; i++) { if (i==3) continue; obj[i] = 'new'; assertEquals(obj[i], 'new'); } }; obj = [undefined, null, 1, , -1, 'a', Symbol("test")]; assertTrue(%HasHoleyElements(obj)); Object.seal(obj); testHoleySealedArray1(obj); // Verify after transition from preventExtensions obj = [undefined, null, 1, , -1, 'a', Symbol("test")]; assertTrue(%HasHoleyElements(obj)); Object.preventExtensions(obj); Object.seal(obj); testHoleySealedArray1(obj); // Verify flat, map, slice, flatMap, join, reduce, reduceRight for sealed holey array function testHoleySealedArray2(arr) { assertTrue(Object.isSealed(arr)); assertFalse(Object.isFrozen(arr)); assertEquals(arr.map(x => [x]), [, ['a'], ['b'], ['c']]); assertEquals(arr.flatMap(x => [x]), ["a", "b", "c"]); assertEquals(arr.flat(), ["a", "b", "c"]); assertEquals(arr.join('-'), "-a-b-c"); const reducer = (accumulator, currentValue) => accumulator + currentValue; assertEquals(arr.reduce(reducer), "abc"); assertEquals(arr.reduceRight(reducer), "cba"); assertEquals(arr.slice(0, 1), [,]); assertEquals(arr.slice(1, 2), ["a"]); // Verify change content of sealed holey array assertThrows(function(){arr.sort();}, TypeError); assertEquals(arr.join(''), "abc"); assertThrows(function(){arr.reverse();}, TypeError); assertEquals(arr.join(''), "abc"); assertThrows(function(){arr.copyWithin(0, 1, 2);}, TypeError); assertEquals(arr.join(''),"abc"); arr.copyWithin(1, 2, 3); assertEquals(arr.join(''),"bbc"); assertThrows(function(){arr.fill('d');}, TypeError); assertEquals(arr.join(''), "bbc"); } var arr1 = [, 'a', 'b', 'c']; assertTrue(%HasHoleyElements(arr1)); Object.seal(arr1); testHoleySealedArray2(arr1); var arr2 = [, 'a', 'b', 'c']; assertTrue(%HasHoleyElements(arr2)); Object.preventExtensions(arr2); Object.seal(arr2); testHoleySealedArray2(arr2); // Test regression with Object.defineProperty var obj = ['a', , 'b']; obj.propertyA = 42; obj[0] = true; Object.seal(obj); assertDoesNotThrow(function() { Object.defineProperty(obj, 'propertyA', { value: obj, }); }); assertEquals(obj, obj.propertyA); assertDoesNotThrow(function() { Object.defineProperty(obj, 'propertyA', { value: obj, writable: false, }); }); obj.propertyA = 42; assertEquals(obj.propertyA, 42); assertThrows(function() { Object.defineProperty(obj, 'abc', { value: obj, }); }, TypeError); // Regression test with simple holey array var arr = [, 'a']; Object.seal(arr); arr[1] = 'b'; assertEquals(arr[1], 'b'); arr[0] = 1; assertEquals(arr[0], undefined); // Test regression Array.concat with double var arr = ['a', , 'b']; Object.seal(arr); arr = arr.concat(0.5); assertEquals(arr, ['a', ,'b', 0.5]); Object.seal(arr); arr = arr.concat([1.5, 'c']); assertEquals(arr, ['a', ,'b', 0.5, 1.5, 'c']); // Regression test with change length var arr = ['a', ,'b']; Object.seal(arr); assertEquals(arr.length, 3); arr.length = 4; assertEquals(arr.length, 4); arr[3] = 'c'; assertEquals(arr[3], undefined); arr.length = 2; assertEquals(arr.length, 3); // Change length with holey entries at the end var arr = ['a', ,]; Object.seal(arr); assertEquals(arr.length, 2); arr.length = 0; assertEquals(arr.length, 1); arr.length = 3; assertEquals(arr.length, 3); arr.length = 0; assertEquals(arr.length, 1);