Object.freeze()
Freezes an object, preventing new properties and changes to existing ones.
Syntax
Object.freeze(obj)Parameters
| Name | Type | Required | Description |
|---|---|---|---|
obj | object | Yes | The object to freeze. |
Returns
object — The same object, now frozen.
Examples
const o = Object.freeze({ a: 1 });
o.a = 2;
console.log(o.a);
Output
1
const o = Object.freeze({ nested: { x: 1 } });
o.nested.x = 9;
console.log(o.nested.x);
Output
9
Notes
A shallow freeze - nested objects can still be mutated. Mutating a frozen
object fails silently in sloppy mode and throws in strict mode. Use
`Object.isFrozen` to test.
Browser & runtime support
| Environment | Since version |
|---|---|
| chrome | 6 |
| firefox | 4 |
| safari | 5.1 |
| edge | 12 |
| node | 0.10 |