根据MDN https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/handler/set,
handler.set()可以捕获继承的属性赋值：
Object.create(proxy)[foo] = bar;
在这种情况下，如何既监视又允许对继承对象进行本地分配？
var base = {
foo: function(){
return "foo";
}
}
var proxy = new Proxy(base, {
set: function(target, property, value, receiver){
console.log("called: " + property + " = " + value, "on", receiver);
//receiver[property] = value; //Infinite loop!?!?!?!?!
//target[property] = value // This is incorrect -> it will set the property on base.
/*
Fill in code here.
*/
return true;
}
})
var inherited = {}
Object.setPrototypeOf(inherited, Object.create(proxy));
inherited.bar = function(){
return "bar";
}
//Test cases
console.log(base.foo); //function foo
console.log(base.bar); //undefined
console.log(inherited.hasOwnProperty("bar")) //true
经过一些额外的思考，我注意到它拦截了 3 个操作：
属性分配： proxy[foo] = bar 和 proxy.foo = bar
继承属性赋值：Object.create(proxy)[foo] = bar
反射.set()
but not Object.defineProperty() https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty这似乎比 = 运算符的级别还要低。
因此，以下工作：
var base = {
foo: function(){
return "foo";
}
};
var proxy = new Proxy(base, {
set: function(target, property, value, receiver){
var p = Object.getPrototypeOf(receiver);
Object.defineProperty(receiver, property, { value: value }); // ***
return true;
}
});
var inherited = {};
Object.setPrototypeOf(inherited, Object.create(proxy));
inherited.bar = function(){
return "bar";
};
// Test cases
console.log(base.foo); // function foo
console.log(base.bar); // undefined
console.log(inherited.bar); // function bar
console.log(inherited.hasOwnProperty("bar")) // true
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