test/mjsunit/object-seal.js

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// Tests the Object.seal and Object.isSealed methods - ES 15.2.3.9 and
// ES 15.2.3.12


// Test that we throw an error if an object is not passed as argument.
var non_objects = new Array(undefined, null, 1, -1, 0, 42.43);
for (var key in non_objects) {
  try {
    Object.seal(non_objects[key]);
    assertUnreachable();
  } catch(e) {
    assertTrue(/Object.seal called on non-object/.test(e));
  }
}

for (var key in non_objects) {
  try {
    Object.isSealed(non_objects[key]);
    assertUnreachable();
  } catch(e) {
    assertTrue(/Object.isSealed called on non-object/.test(e));
  }
}

// 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))