调用函数和引用函数之间的区别？ [英] Difference between calling function and referencing function?

问题描述

查看以下代码：

window.onload = someFunction;

很多时候我看到使用这种代码甚至我都使用相同的代码。但是，仍有一些事情尚不清楚。

Many times I see the use of this kind of code and even I use the same. But, there are still few things unclear.

1. 上面是一旦页面加载就调用 someFunction 。但是，我们不应该用括号（）来调用函数吗？


2. 根据我的理解，我们只是分配 someFunction 到 window.onload ，因此我们可以或不应该调用 window.onload（） ;


3. 是否有这种情况，当 functionName（）和 functionName becames可互换。因为在很多地方和各种API，我看到调用函数没有括号。

1. The above is a call to someFunction as soon as the page loads, right. But, aren't we supposed to call a function with brackets ()?
2. From my understanding, we are just assigning someFunction to window.onload, therefore can we or shouldn't we call window.onload();
3. Are there such cases, when functionName() and functionName becames interchangeable. Because at many places, and in various API, I have seen calling the function without brackets.

推荐答案

你不是调用这个函数，你告诉浏览器 调用哪个函数，onload。

You're not calling the function, you're telling the browser which function to call, onload.

引用函数并调用函数永远不可互换：它们完全不同。

Referencing a function and calling a function are never interchangeable: they're completely different things.

但是，您可以调用返回的函数 a function：

You may, however, call a function that returns a function:

function getFunction() {
    return function() {
        alert("I'm the real onload function.");
    };
}

window.onload = getFunction();

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