扩展功能 - 合并两个功能？ [英] Extend a function - merge two functions?

问题描述

我现在处于一个新的领域，我有一段时间没有处理过这种事情。

I am in some new territory now, I haven't worked with this sort of thing in a while.

获得Javascript的最佳方式是什么？ class'例如

What is the best way to have a Javascript 'class' for instance

// In the parent instance
function xyz()
{
    var x = 1;
}

我想在课堂上设置这个，当用户扩展课程时，我希望他们有效地扩展这个功能。我知道我不清楚，但这是漫长的一天。例如，这是用户的代码。

I want to set this in the class, and when a user extends a class, I want them to effectively be extending this function. I know I'm not being clear, but it's been a long day. This is the user's code for instance.

// In the child instance
function xyz()
{
    var y = 2;
}

合并应该导致：

// In the merged instance
function xyz()
{
    var x = 1;
    var y = 2;
}

我吸错了什么或提出错误的问题？

Am I smoking the wrong stuff or asking the wrong question?

推荐答案

你不能像在那里描述的那样合并函数，但你可以做的是重新定义一个函数来调用它们本身和一个新函数（在原始函数之前或之后）。

You can't 'merge' functions as you describe them there, but what you can do is have one function be redefined to call both itself and a new function (before or after the original).

var xyz = function(){
   console.log('xyz');
};

var abc = function(){
   console.log('abc');
};

// and, elsewhere, if you want to merge:
var orig = abc;
abc = function(){
    orig.call(this, arguments);
    xyz.call(this, arguments);
};

如果您不关心执行上下文或者不需要包含（this，arguments）如果被调用的函数是无参数的。但是，如果你想要一个参数化的方法，那么为了清楚说明你可能会做什么，我将其包括在内。

The inclusion of (this, arguments) is not needed if you don't care about execution context or if the called function is parameterless. But I included for clarity of what one might do if you wanted a parameterized method.

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