有没有办法捕获尝试访问不存在的属性或方法？ [英] Is there a way to catch an attempt to access a non existant property or method?

问题描述

例如这段代码：

function stuff() {
  this.onlyMethod = function () {
    return something;
  }
}

// some error is thrown
stuff().nonExistant();

有没有办法做一些像PHP的 __ call 作为对象内部的后退？

Is there a way to do something like PHP's __call as a fallback from inside the object?

function stuff() {
  this.onlyMethod = function () {
    return something;
  }
  // "catcher" function
  this.__call__ = function (name, params) {
    alert(name + " can't be called.");
  }
}

// would then raise the alert "nonExistant can't be called".
stuff().nonExistant();

也许我会解释一下我正在做的事情。

该对象包含另一个对象，该对象具有应该可以通过此对象直接访问的方法。但是这些方法对于每个对象都是不同的，所以我不能只是路由它们，我需要能够动态地调用它们。

The object contains another object, which has methods that should be accessible directly through this object. But those methods are different for each object, so I can't just route them, i need to be able to call them dynamically.

我知道我可以做到其中的对象是主对象的属性 stuff.obj.existant（），但我只是想知道我是否可以避免它，因为主要对象是一种类型的只是暂时添加一些功能的包装器（并且可以更容易地同时访问对象）。

I know I could just make the object inside it a property of the main object stuff.obj.existant(), but I'm just wondering if I could avoid it, since the main object is sort of a wrapper that just adds some functionality temporarily (and makes it easier to access the object at the same time).

推荐答案

有一个为不存在的方法调用定义通用处理程序的方法，但它是非标准的。查看Firefox的 noSuchMethod 。将允许您动态地将调用路由到未定义的方法。似乎v8也是获得支持。

There is a way to define a generic handler for calls on non-existant methods, but it is non-standard. Checkout the noSuchMethod for Firefox. Will let you route calls to undefined methods dynamically. Seems like v8 is also getting support for it.

要使用它，请在任何对象上定义此方法：

To use it, define this method on any object:

var a = {};

a.__noSuchMethod__ = function(name, args) {
    console.log("method %s does not exist", name);
};

a.doSomething(); // logs "method doSomething does not exist"

但是，如果你想要一个跨浏览器的方法，然后简单的try-catch阻止如果要走的路：

However, if you want a cross-browser method, then simple try-catch blocks if the way to go:

try {
    a.doSomething();
}
catch(e) {
    // do something
}

如果你不想在整个代码中编写try-catch，那么你可以在主对象中添加一个包装器，通过它来路由所有函数调用。

If you don't want to write try-catch throughout the code, then you could add a wrapper to the main object through which all function calls are routed.

function main() {
    this.call = function(name, args) {
        if(this[name] && typeof this[name] == 'function') {
            this[name].call(args);
        }
        else {
            // handle non-existant method
        }
    },
    this.a = function() {
        alert("a");
    }
}

var object = new main();
object.call('a') // alerts "a"
object.call('garbage') // goes into error-handling code

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