无法读取undefined属性'apply' [英] Cannot read property 'apply ' of undefined

问题描述

我正在尝试理解.apply方法。所以，我创建了以下代码：

I am trying to understand the .apply-method. So, I created the following code:

var o = new Object();
o.method = function(x, y) {
  return x + y
};

o.method = (function(original) {
  return function(x, y) {
    var a = 'A';
    var b = 'B';
    var result = original.apply(this, [a, b]);
    return result;
  }
})(o.method);

console.log(o.method(1, 2));

我认为最后一个打开和关闭的括号可能为空，因此调用方法o.method自动。但是空括号

I thought that the last open and close parentheses could be empty and so the method o.method is invoked automatically. But with empty parentheses

o.method = (function(original) {
  return function(x, y) {
    var a = 'A';
    var b = 'B';
    var result = original.apply(this, [a, b]);
    return result;
  }
})();

o.method(1, 2);

我收到以下错误：
无法读取属性'apply'of undefined

I get the following error: Cannot read property 'apply' of undefined

有人可以解释一下为什么吗？

Can someone please explain me why?

亲切的问候
Henning

Kind regards Henning

推荐答案

通过一些更改，您的代码是正确的：

With some change your code is correct:

var o = new Object();
o.method2 = function(x,y){return x+y};

o.method = (function (original){
    return function(x,y){
            var result = original.call(this, x,y);
        return result;
    }
})(o.method2);

同样适用于测试和运行：

Also for test and run:

o.method(2,3)

结果为5

还有申请：

var o = new Object();
o.method2 = function(x,y){return x+y};

o.method = (function (original){
    return function(x,y){
            var result = original.apply(this, [x,y]);
        return result;
    }
})(o.method2);

然后测试：

o.method(2,3)

结果为5

有关call（）和apply（）用法的更多信息，请阅读以下文章：
http://adripofjavascript.com/blog/drips/invoking-javascript-functions-with-call-and-apply .html

For more information about the usage of call() and apply() you can read this article: http://adripofjavascript.com/blog/drips/invoking-javascript-functions-with-call-and-apply.html

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