Object.seal()
Seals an object, preventing new properties and making existing ones non-configurable.
Syntax
Object.seal(obj)Parameters
| Name | Type | Required | Description |
|---|---|---|---|
obj | object | Yes | The object to seal. |
Returns
object — The same object, now sealed.
Examples
const o = Object.seal({ a: 1 });
o.a = 2; // allowed
o.b = 3; // ignored
console.log(o);
Output
{ a: 2 }
console.log(Object.isSealed(Object.seal({})));
Output
true
Notes
Unlike `freeze`, existing writable properties can still be reassigned; you
just cannot add or delete properties or reconfigure them. Shallow operation.
Browser & runtime support
| Environment | Since version |
|---|---|
| chrome | 6 |
| firefox | 4 |
| safari | 5.1 |
| edge | 12 |
| node | 0.10 |