handler.setPrototypeOf()
方法主要用来拦截 Object.setPrototypeOf()
.
语法
var p = new Proxy(target, { setPrototypeOf: function(target, prototype) { } });
参数
以下参数传递给 setPrototypeOf
方法.
-
target
- 被拦截目标对象.
-
prototype
-
对象新原型或为
null
.
返回值
如果成功修改了[[Prototype]]
, setPrototypeOf
方法返回 true
,否则返回 false
.
描述
这个 handler.setPrototypeOf
方法用于拦截 Object.setPrototypeOf()
.
拦截
这个方法可以拦截以下操作:
Invariants
如果违反了下列规则,则proxy将抛出一个TypeError
:
如果 target
不可扩展, 原型参数必须与Object.getPrototypeOf(target)
的值相同.
示例
如果你不想为你的对象设置一个新的原型,你的handler's的setPrototypeOf
方法可以返回false,也可以抛出异常。
The former approach means that any operation that performs such mutation, that throws an exception on failure to mutate, will have to create the exception itself. For example, Reflect.setPrototypeOf()
, no exception will be thrown.
var handlerReturnsFalse = { setPrototypeOf(target, newProto) { return false; } }; var newProto = {}, target = {}; var p1 = new Proxy(target, handlerReturnsFalse); Object.setPrototypeOf(p1, newProto); // throws a TypeError Reflect.setPrototypeOf(p1, newProto); // returns false
The latter approach will cause any operation that attempts to mutate, to throw. This approach is required if you want even non-throwing operations to throw on failure, or you want to throw a custom exception value.
var handlerThrows = { setPrototypeOf(target, newProto) { throw new Error('custom error'); } }; var newProto = {}, target = {}; var p2 = new Proxy(target, handlerThrows); Object.setPrototypeOf(p2, newProto); // throws new Error("custom error") Reflect.setPrototypeOf(p2, newProto); // throws new Error("custom error")
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) [[SetPrototypeOf]] |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) [[SetPrototypeOf]] |
Draft |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
setPrototypeOf |
Chrome Full support 49 | Edge Full support 12 | Firefox Full support 49 | IE No support No | Opera Full support 36 | Safari ? | WebView Android Full support 49 | Chrome Android Full support 49 | Firefox Android Full support 49 | Opera Android Full support 36 | Safari iOS ? | Samsung Internet Android Full support 5.0 | nodejs Full support 6.0.0 |
Legend
- Full support
- Full support
- No support
- No support
- Compatibility unknown
- Compatibility unknown