在代理处理程序中，如何取消获取属性（var）与调用方法？ [英] In the Proxy handler, how to distiguish getting a property (var) vs calling a method?
问题描述
我有以下代码，我正在使用代理对象（代理）来尝试捕获方法调用和访问属性：
I have the following code, where I'm using Proxy object (proxy) to try to catch method calls and access of the properties:
示例： https://jsfiddle.net/r8j4fzxL/2/
(function() {
'use strict';
console.clear();
//some empty class where I want to trap methods props
class X {
//...
}
let proxy = {
get: function(target, prop, receiver) {
console.log('get called: ',
'target:', target,
'prop:', prop,
'receiver:', receiver
);
//this is OK, if we are called as a method.
//but it isn't when called as .prop - because, obviously, we return a function here.
return function(...args) {
console.log('wrapper args:', args);
return 42;
}
},
};
let p1 = new Proxy(X, proxy);
//how to distinguish the two in the above proxy:
console.log(p1.test('some arg passed'));
console.log(p1.test);
})();
我在这里有两个问题。
-
一般来说，如果我想同时捕获属性访问权限和方法访问权限，这是正确的方法吗？或者也许我应该以某种方式使用.apply陷阱（虽然没有这样做）？
Generally, is this the right way, if I want to trap both properties access and method access? Or maybe should I go with .apply trap somehow (failed to do so though)?
如果这是正确的方式（使用.get） - 那么如何我知道用户如何访问...的事情？通过 .foo; 或通过 .foo（）;？
If this is the right way (using .get) - then how do I know how the user accessed the... thing? Via .foo; or via .foo();?
我使用的资源显然并不完全明白：
Resources I used and apparently didn't fully understand:
- MDN docs: Proxy
- MDN docs: handler.get()
- MDN docs: handler.apply()
SO：< a href =https://stackoverflow.com/questions/10226064/javascript-equivalent-of-php-call> PHP等效的PHP __call
推荐答案
代理本质上是一种对象，它暴露出一种编程方式来挂钩对象可以运行的操作ave对他们进行了表演。以此为基础，无法在访问属性时将属性访问与属性访问+调用区分开来。返回值是函数的事实就是您可以知道的。
Proxies are essentially objects that expose a programmatic way to hook into the operations that objects can have performed on them. With that as a base, there is no way to distinguish a property access from a property access + call, at the point where the property is accessed. The fact that the returned value is a function is all that you can know.
从语言的角度来看， p.foo（）分解为
From the standpoint of the language, p.foo() breaks down into
var p = ...
var foo = p.foo;
foo.apply(p, []);
为例。 p.foo 实际上不会访问 .apply ，但重点是属性访问完全独立于如何实际使用/调用返回的值。
as an example. p.foo wouldn't actually access .apply, but the point is that the property access is entirely independent of how the returned value is actually used/called.
所以你的选择主要是检查 test的值是否已经是一个函数，如果是这样，请用您的包装器包装该值。如果它不是一个函数，你似乎想要跳过它。例如
So you option would essentially be to check whether the value of test was already a function, and if so, wrap that value with your wrapper. If it was not a function, it seems like you'll want to skip wrapping it. e.g.
get: function(target, prop, receiver) {
var value = Reflect.get(target, prop, receiver);
if (typeof value === "function") {
return function(...args) {
// probably call 'value' with whatever you need
};
} else {
// return the origin value.
return value;
}
}
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