Nossos voluntários ainda não traduziram este artigo para o Português (do Brasil) . Junte-se a nós e ajude a fazer o trabalho!
Você também pode ler o artigo em English (US).

The Object.isFrozen() determines if an object is frozen.

Syntax

Object.isFrozen(obj)

Parameters

obj
The object which should be checked.

Return value

A Boolean indicating whether or not the given object is frozen.

Description

An object is frozen if and only if it is not extensible, all its properties are non-configurable, and all its data properties (that is, properties which are not accessor properties with getter or setter components) are non-writable.

Examples

// A new object is extensible, so it is not frozen.
Object.isFrozen({}); // === false

// An empty object which is not extensible
// is vacuously frozen.
var vacuouslyFrozen = Object.preventExtensions({});
Object.isFrozen(vacuouslyFrozen); // === true

// A new object with one property is also extensible,
// ergo not frozen.
var oneProp = { p: 42 };
Object.isFrozen(oneProp); // === false

// Preventing extensions to the object still doesn't 
// make it frozen, because the property is still 
// configurable (and writable).
Object.preventExtensions(oneProp);
Object.isFrozen(oneProp); // === false

// ...but then deleting that property makes the object
// vacuously frozen.
delete oneProp.p;
Object.isFrozen(oneProp); // === true

// A non-extensible object with a non-writable
// but still configurable property is not frozen.
var nonWritable = { e: 'plep' };
Object.preventExtensions(nonWritable);
Object.defineProperty(nonWritable, 'e', {
  writable: false
}); // make non-writable
Object.isFrozen(nonWritable); // === false

// Changing that property to non-configurable
// then makes the object frozen.
Object.defineProperty(nonWritable, 'e', {
  configurable: false
}); // make non-configurable
Object.isFrozen(nonWritable); // === true

// A non-extensible object with a non-configurable
// but still writable property also isn't frozen.
var nonConfigurable = { release: 'the kraken!' };
Object.preventExtensions(nonConfigurable);
Object.defineProperty(nonConfigurable, 'release', {
  configurable: false
});
Object.isFrozen(nonConfigurable); // === false

// Changing that property to non-writable
// then makes the object frozen.
Object.defineProperty(nonConfigurable, 'release', {
  writable: false
});
Object.isFrozen(nonConfigurable); // === true

// A non-extensible object with a configurable
// accessor property isn't frozen.
var accessor = { get food() { return 'yum'; } };
Object.preventExtensions(accessor);
Object.isFrozen(accessor); // === false

// ...but make that property non-configurable
// and it becomes frozen.
Object.defineProperty(accessor, 'food', {
  configurable: false
});
Object.isFrozen(accessor); // === true

// But the easiest way for an object to be frozen
// is if Object.freeze has been called on it.
var frozen = { 1: 81 };
Object.isFrozen(frozen); // === false
Object.freeze(frozen);
Object.isFrozen(frozen); // === true

// By definition, a frozen object is non-extensible.
Object.isExtensible(frozen); // === false

// Also by definition, a frozen object is sealed.
Object.isSealed(frozen); // === true

Notes

In ES5, if the argument to this method is not an object (a primitive), then it will cause a TypeError. In ES2015, a non-object argument will be treated as if it was a frozen ordinary object, simply return true.

Object.isFrozen(1);
// TypeError: 1 is not an object (ES5 code)

Object.isFrozen(1);
// true                          (ES2015 code)

Specifications

Specification Status Comment
ECMAScript 5.1 (ECMA-262)
The definition of 'Object.isFrozen' in that specification.
Standard Initial definition. Implemented in JavaScript 1.8.5.
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Object.isFrozen' in that specification.
Standard  
ECMAScript Latest Draft (ECMA-262)
The definition of 'Object.isFrozen' in that specification.
Living Standard  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support6 Yes49125.1
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic support Yes Yes Yes Yes Yes Yes Yes

See also

Etiquetas do documento e colaboradores

 Última atualização por: fscholz,