handler.ownKeys()
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since 2016年9月.
handler.ownKeys() 方法用于拦截 Reflect.ownKeys().
尝试一下
const monster1 = {
_age: 111,
[Symbol("secret")]: "I am scared!",
eyeCount: 4,
};
const handler1 = {
ownKeys(target) {
return Reflect.ownKeys(target);
},
};
const proxy1 = new Proxy(monster1, handler1);
for (const key of Object.keys(proxy1)) {
console.log(key);
// Expected output: "_age"
// Expected output: "eyeCount"
}
语法
js
var p = new Proxy(target, {
ownKeys: function (target) {},
});
参数
下面的参数被传递给 ownKeys。this 被绑定在 handler 上。
target-
目标对象。
返回值
ownKeys 方法必须返回一个可枚举对象。
描述
handler.ownKeys() 方法用于拦截 Reflect.ownKeys().
拦截
该拦截器可以拦截以下操作::
约束
如果违反了下面的约束，proxy 将抛出错误 TypeError:
示例
下面的代码拦截 Object.getOwnPropertyNames().
js
var p = new Proxy(
{},
{
ownKeys: function (target) {
console.log("called");
return ["a", "b", "c"];
},
},
);
console.log(Object.getOwnPropertyNames(p)); // "called"; outputs [ 'a', 'b', 'c' ]
下面的代码违反了约定
js
var obj = {};
Object.defineProperty(obj, "a", {
configurable: false,
enumerable: true,
value: 10,
});
var p = new Proxy(obj, {
ownKeys: function (target) {
return [123, 12.5, true, false, undefined, null, {}, []];
},
});
console.log(Object.getOwnPropertyNames(p));
// TypeError: proxy [[OwnPropertyKeys]] 必须返回一个数组
// 数组元素类型只能是 String 或 Symbol
规范
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-proxy-object-internal-methods-and-internal-slots-ownpropertykeys |
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