JS: Object.seal

By Xah Lee. Date: . Last updated: .
Object.seal(obj)
make a object not able to add properties nor delete properties.
  • Make obj not extensible.
  • Set ALL of the obj's own property's “configurable” attributes to false.
  • Return the modified object obj.

🛑 warning: the parent object may still have properties added or deleted, thus inherit unexpected properties.

// seal a object.

const jj = { p1: 1, p2: 2 };

// configurable attribute for p1 is true
console.assert(
 Reflect.getOwnPropertyDescriptor(jj, "p1").configurable,
);

Object.seal(jj);

// configurable attribute for p1 is now false
console.assert(
 Reflect.getOwnPropertyDescriptor(jj, "p1").configurable === false,
);

// configurable attribute for p2 is now false
console.assert(
 Reflect.getOwnPropertyDescriptor(jj, "p2").configurable === false,
);

// jj is now not extensible
console.assert(
 Reflect.isExtensible(jj) === false,
);