Javascript IIFE作为对象的属性（方法） [英] Javascript IIFE as an object's property (method)

问题描述

我正在尝试使用IIFE作为方法（可能是错误的）。

I'm trying to use an IIFE as a method (which might be wrong).

为什么？因为，我正在尝试实现代理设计模式。

Why ? Because, I'm trying to implement the proxy design pattern.

在adobe扩展脚本中，有一个 app对象可以访问文档，例如-

In adobe extendscript, there is an "app" object to access documents, etc, like -

var length = app.activeDocument.length; // or some other property

现在，我想在 app周围放置一个代理。因此，我创建了一个代理对象-

Now, I wanted to put a proxy around "app". So I created a proxy object -

var AppProxy = {
    activeDocument: function() { // do stuff...; return app.ActiveDocument; }
}

但是现在，这是我必须访问的方式-

But now, this is how I had to access it -

var length = AppProxy.activeDocument().length;

但这是我要访问的方式-

But this is how I want to access it -

var length = AppProxy.activeDocument.length; // no parenthesis

因此，我了解了IIFE，并最终做到了-

So I read about IIFE, and ended up doing this -

var AppProxy = {
    activeDocument: (function() { 
    // do stuff...;
    return app.ActiveDocument; })()
}

和预期的一样， AppProxy 后，即会自动调用> AppProxy.activeDocument 。即，在达到 var length = AppProxy.activeDocument.length 之前。

And as expected, the AppProxy.activeDocument gets called automatically when AppProxy is defined, i.e. even BEFORE it reaches var length = AppProxy.activeDocument.length.

那么当将AppProxy定义为对象文字时，如何防止这种情况发生？
是否可以解决我的要求？

So how do I prevent this from happening when AppProxy is defined as an object literal ? Is there a workaround to my requirement ?

谢谢。

推荐答案

但这是我要访问的方式-

But this is how I want to access it -

var length = AppProxy.activeDocument.length ; //没有括号

为此，您需要定义 activeDocument 作为具有 getter 函数的属性。在具有适当支持的浏览器中可以实现ES5 getter和setter，这是所有现代浏览器（不是IE8和更早版本）。 （在ES5之前，存在一些浏览器支持的从未标准化的语法，但再次不支持IE8或更早版本。）。

To do that, you need to define activeDocument as a property with a getter function. This is possible in browsers with proper support for ES5's getters and setters, which is all modern browsers (not IE8 and earlier). (Before ES5, there was a never-standardized syntax for this that some browsers supported, but again not IE8 or earlier).

在ES5中，您可以使用 Object.defineProperty 或通过在对象初始化程序中定义一个吸气剂。这是 Object.defineProperty ：

In ES5, you can do this either with Object.defineProperty or by defining a getter in an object initializer. Here's Object.defineProperty:

// ES5+ only
var AppProxy = {};
Object.defineProperty(AppProxy, "activeDocument", {
    get: function() {
        // do stuff...;
        return app.ActiveDocument;
    }
});

此处将其作为对象初始化程序的一部分：

Here's doing it as part of the object initializer:

// ES5+ only
var AppProxy = {
    get activeDocument() {
        // do stuff...;
        return app.ActiveDocument;
    }
};

已经做过任何一个，那么：

Having done either of those, then this:

var length = AppProxy.activeDocument.length;

...运行该功能，即使它看起来不一样。函数调用仍然发生，只是被隐藏。

...runs that function, even though it doesn't look like it does. The function call still happens, it's just hidden.

但是如果您需要支持过时的浏览器（即使在2016年中期，IE8仍然占有约5％的市场份额）或如果您不想隐藏正在调用函数的事实，只需调用函数即可：

But if you need to support obsolete browsers (even here in mid 2016, IE8 still has ~5% market share) or if you don't want to hide the fact you're calling a function, just call the function:

var length = AppProxy.activeDocument().length;

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