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27
28// Tests the Object.preventExtensions method - ES 15.2.3.10
29
30
31var obj1 = {};
32// Extensible defaults to true.
33assertTrue(Object.isExtensible(obj1));
34Object.preventExtensions(obj1);
35
36// Make sure the is_extensible flag is set.
37assertFalse(Object.isExtensible(obj1));
38obj1.x = 42;
39assertEquals(undefined, obj1.x);
40
41// Try adding a new element.
42obj1[1] = 42;
43assertEquals(undefined, obj1[1]);
44
45
46// Try when the object has an existing property.
47var obj2 = {};
48assertTrue(Object.isExtensible(obj2));
49obj2.x = 42;
50assertEquals(42, obj2.x);
51assertTrue(Object.isExtensible(obj2));
52
53Object.preventExtensions(obj2);
54assertEquals(42, obj2.x);
55
56obj2.y = 42;
57// obj2.y should still be undefined.
58assertEquals(undefined, obj2.y);
59// Make sure we can still write values to obj.x.
60obj2.x = 43;
61assertEquals(43, obj2.x)
62
63obj2.y = new function() { return 42; };
64// obj2.y should still be undefined.
65assertEquals(undefined, obj2.y);
66assertEquals(43, obj2.x)
67
68try {
69  Object.defineProperty(obj2, "y", {value: 42});
70} catch (e) {
71  assertTrue(/object is not extensible/.test(e));
72}
73
74// obj2.y should still be undefined.
75assertEquals(undefined, obj2.y);
76assertEquals(43, obj2.x);
77
78obj2[1] = 42;
79assertEquals(undefined, obj2[1]);
80
81var arr = new Array();
82arr[1] = 10;
83
84Object.preventExtensions(arr);
85
86arr[2] = 42;
87assertEquals(10, arr[1]);
88
89// We should still be able to change exiting elements.
90arr[1]= 42;
91assertEquals(42, arr[1]);
92
93
94// Test the the extensible flag is not inherited.
95var parent = {};
96parent.x = 42;
97Object.preventExtensions(parent);
98
99var child = Object.create(parent);
100
101// We should be able to add new properties to the child object.
102child.y = 42;
103
104// This should have no influence on the parent class.
105parent.y = 29;
106
107
108// Test that attributes on functions are also handled correctly.
109function foo() {
110  return 42;
111}
112
113Object.preventExtensions(foo);
114
115foo.x = 29;
116assertEquals(undefined, foo.x);
117
118// when Object.isExtensible(o) === false
119// assignment should return right hand side value
120var o = Object.preventExtensions({});
121var v = o.v = 50;
122assertEquals(undefined, o.v);
123assertEquals(50, v);
124
125// test same behavior as above, but for integer properties
126var n = o[0] = 100;
127assertEquals(undefined, o[0]);
128assertEquals(100, n);
129