Object.seal()
方法封闭一个对象,阻止添加新属性并将所有现有属性标记为不可配置。当前属性的值只要可写就可以改变。
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语法
Object.seal(obj)
参数
-
obj
- 将要被密封的对象。
返回值
被密封的对象。
描述
通常,一个对象是严格模式 中最常见的,但不唯一)。
不会影响从原型链上继承的属性。但 ) 属性的值也会不能修改。
返回被密封对象的引用。
例子
var obj = { prop: function() {}, foo: 'bar' }; // New properties may be added, existing properties // may be changed or removed. obj.foo = 'baz'; obj.lumpy = 'woof'; delete obj.prop; var o = Object.seal(obj); o === obj; // true Object.isSealed(obj); // === true // Changing property values on a sealed object // still works. obj.foo = 'quux'; // But you can't convert data properties to accessors, // or vice versa. Object.defineProperty(obj, 'foo', { get: function() { return 'g'; } }); // throws a TypeError // Now any changes, other than to property values, // will fail. obj.quaxxor = 'the friendly duck'; // silently doesn't add the property delete obj.foo; // silently doesn't delete the property // ...and in strict mode such attempts // will throw TypeErrors. function fail() { 'use strict'; delete obj.foo; // throws a TypeError obj.sparky = 'arf'; // throws a TypeError } fail(); // Attempted additions through // Object.defineProperty will also throw. Object.defineProperty(obj, 'ohai', { value: 17 }); // throws a TypeError Object.defineProperty(obj, 'foo', { value: 'eit' }); // changes existing property value
注意
在ES5中,如果这个方法的参数不是一个(原始)对象,那么它将导致TypeError
。在ES2015中,非对象参数将被视为已被密封的普通对象,会直接返回它。
Object.seal(1); // TypeError: 1 is not an object (ES5 code) Object.seal(1); // 1 (ES2015 code)
对比 Object.freeze()
使用Object.freeze()
冻结的对象中的现有属性是不可变的。用Object.seal()
密封的对象可以改变其现有属性。
规范
Specification | Status | Comment |
---|---|---|
ECMAScript 5.1 (ECMA-262) Object.seal |
Standard | Initial definition. Implemented in JavaScript 1.8.5. |
ECMAScript 2015 (6th Edition, ECMA-262) Object.seal |
Standard | |
ECMAScript Latest Draft (ECMA-262) Object.seal |
Draft |
浏览器兼容
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.
Update compatibility data on GitHub
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
seal |
Chrome Full support 6 | Edge Full support 12 | Firefox Full support 4 | IE Full support 9 | Opera Full support 12 | Safari Full support 5.1 | WebView Android Full support Yes | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes | nodejs Full support Yes |
Legend
- Full support
- Full support