JavaScript (ES2026) reference · Object Methods

JavaScript Object.freeze() Method

Make an object immutable: no properties can be added, removed or changed. The freeze is shallow.

JavaScript (ES2026) Since ES5

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Syntax

Object.freeze(obj)

Parameters

Parameter	Description
`obj`	The object to inspect or change.

Return value

The same object, now frozen.

Examples

Constants that can't changeTry it yourself

"use strict";
const ROLES = Object.freeze({ ADMIN: "admin", USER: "user" });
try { ROLES.ADMIN = "root"; } catch (e) { console.log(e.constructor.name); }
console.log(ROLES.ADMIN, Object.isFrozen(ROLES));

Output

TypeError
admin true

Freezing is shallowTry it yourself

const cfg = Object.freeze({ db: { host: "localhost" } });
cfg.db.host = "changed"; // nested objects aren't frozen
console.log(cfg.db.host);