參考：handler.get()

簡單的例子：

let p = new Proxy({}, {
	get: function(target, name, receiver) {
		console.log('object been proxied', target);
		console.log('accessed name', name);
		console.log('parent:', receiver === p);
		console.log('child(a):', !!a?receiver === a:null);
		return 'ok\n====';
	}
});
let A = function() {};
A.prototype = p;
let a = new A();
console.log(a.c);
console.log(p.c);

只是示範一下receiver是參考到哪個物件。如果直接使用proxy，就會指到proxy。但是如果是繼承了proxy的物件，那會指到該物件。

上例console.log(a.c);結果是：

object been proxied {}
accessed name c
parent: false
child(a): true
ok
====

所以receiver是指到a。

而console.log(p.c);結果是：

object been proxied {}
accessed name c
parent: true
child(a): false
ok
====

所以receiver是指到p。