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• 句法
• 描述
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

Object.isSealed() method determines if an object is sealed.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

句法

Object.isSealed(obj)
					

参数

obj

The object which should be checked.

返回值

A 布尔 indicating whether or not the given object is sealed.

描述

返回 true if the object is sealed, otherwise false . An object is sealed if it is not extensible and if all its properties are non-configurable and therefore not removable (but not necessarily non-writable).

范例

Using Object.isSealed

// Objects aren't sealed by default.
var empty = {};
Object.isSealed(empty); // === false
// If you make an empty object non-extensible,
// it is vacuously sealed.
Object.preventExtensions(empty);
Object.isSealed(empty); // === true
// The same is not true of a non-empty object,
// unless its properties are all non-configurable.
var hasProp = { fee: 'fie foe fum' };
Object.preventExtensions(hasProp);
Object.isSealed(hasProp); // === false
// But make them all non-configurable
// and the object becomes sealed.
Object.defineProperty(hasProp, 'fee', {
  configurable: false
});
Object.isSealed(hasProp); // === true
// The easiest way to seal an object, of course,
// is Object.seal.
var sealed = {};
Object.seal(sealed);
Object.isSealed(sealed); // === true
// A sealed object is, by definition, non-extensible.
Object.isExtensible(sealed); // === false
// A sealed object might be frozen,
// but it doesn't have to be.
Object.isFrozen(sealed); // === true
// (all properties also non-writable)
var s2 = Object.seal({ p: 3 });
Object.isFrozen(s2); // === false
// ('p' is still writable)
var s3 = Object.seal({ get p() { return 0; } });
Object.isFrozen(s3); // === true
// (only configurability matters for accessor properties)
					

Non-object coercion

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 sealed ordinary object, simply return true .

Object.isSealed(1);
// TypeError: 1 is not an object (ES5 code)
Object.isSealed(1);
// true                          (ES2015 code)
					

规范

规范
ECMAScript (ECMA-262) The definition of 'Object.isSealed' in that specification.

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
isSealed	Chrome 6	Edge 12	Firefox 4	IE 9	Opera 12	Safari 5.1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 12	Safari iOS 6	Samsung Internet Android 1.0	nodejs Yes

图例

完整支持

完整支持

另请参阅

• Object.seal()
• Object.preventExtensions()
• Object.isExtensible()
• Object.freeze()
• Object.isFrozen()

元数据

• 最后修改： May 8, 2020

相关话题

1. 标准内置对象
2. Object
3. 特性
   1. Object.prototype.__proto__
   2. Object.prototype.constructor
4. 方法
   1. Object.assign()
   2. Object.create()
   3. Object.defineProperties()
   4. Object.defineProperty()
   5. Object.entries()
   6. Object.freeze()
   7. Object.fromEntries()
   8. Object.getOwnPropertyDescriptor()
   9. Object.getOwnPropertyDescriptors()
   10. Object.getOwnPropertyNames()
   11. Object.getOwnPropertySymbols()
   12. Object.getPrototypeOf()
   13. Object.is()
   14. Object.isExtensible()
   15. Object.isFrozen()
   16. Object.isSealed()
   17. Object.keys()
   18. Object.preventExtensions()
   19. Object.prototype.__defineGetter__()
   20. Object.prototype.__defineSetter__()
   21. Object.prototype.__lookupGetter__()
   22. Object.prototype.__lookupSetter__()
   23. Object.prototype.hasOwnProperty()
   24. Object.prototype.isPrototypeOf()
   25. Object.prototype.propertyIsEnumerable()
   26. Object.prototype.toLocaleString()
   27. Object.prototype.toSource()
   28. Object.prototype.toString()
   29. Object.prototype.valueOf()
   30. Object.seal()
   31. Object.setPrototypeOf()
   32. Object.values()
5. 继承：
6. Function
7. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
8. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()