var twice = {
apply (target, ctx, args) {
console.log("apply:" + target);
return Reflect.apply(...arguments) * 2;
}
};
var sum = {
ss(){
console.log("sum ss()");
return 200;
}
};
var proxy = new Proxy(sum, twice);
//这里为什么不会打印出 console.log("apply:" + target);
//只打印 console.log("sum ss()");
proxy.ss();
apply
只能拦截对 proxy
本身的调用,不能拦截对 proxy
下面的方法的调用:
This trap can intercept these operations:
proxy(...args)
Function.prototype.apply() and Function.prototype.call()
Reflect.apply()
via https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/handler/apply
你仔细想想 JavaScript 这种「函数为一等公民」的设计,就会发现这样是有道理的。
不过,你可以这么 workaround:
var twice = {
get (target, property, receiver) {
return () => (Reflect.apply(target[property], target, arguments) * 2);
}
};
var sum = {
ss () {
console.log("sum ss()");
return 200;
}
};
var proxy = new Proxy(sum, twice);
proxy.ss();
sum
又不是函数,怎么能在twice
里用apply
? 应该用get
var twice = {
get (target, ctx, args) {
console.log("apply:" + target);
return function(){
return target[ctx]() * 2;
};
}
};
var sum = {
ss(){
console.log("sum ss()");
return 200;
}
};
var proxy = new Proxy(sum, twice);
//这里为什么不会打印出 console.log("apply:" + target);
//只打印 console.log("sum ss()");
console.log(proxy.ss());