JavaScript (ES2026) reference · Object Methods

JavaScript Object.isFrozen() Method

Return true if an object is frozen: no properties can be added, removed or changed.

JavaScript (ES2026) Since ES5

Create a free account to save this page, take notes and track your progress. Sign in

Syntax

Object.isFrozen(obj)

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

true or false.

Frozen or notTry it yourself

const a = Object.freeze({ x: 1 });
console.log(Object.isFrozen(a), Object.isFrozen({ x: 1 }));

Output

true false

Primitives and empty non-extensible objects count as frozenTry it yourself

console.log(Object.isFrozen("text"), Object.isFrozen(Object.preventExtensions({})));

Output

true true

Version	Change
JavaScript ES5	Added

Object.freeze() · Make an object immutable: no properties can be added, removed or changed. The freeze is shallow.
Object.isSealed() · Return true if an object is sealed: properties can't be added or removed, but existing ones may still change.
JavaScript Objects · tutorial