为什么JavaScript函数声明（和表达式）？ [英] Why JavaScript function declaration (and expression)?

问题描述

我见过其他人使用以下模式。

I've seen others using the following pattern.

var bar = function foo(){};
console.log(bar); // foo()
console.log(foo); // ReferenceError: foo is not defined

但为什么？如果两者都被宣布，我可以看到这一点，但事实并非如此。原因是什么？

But why? I can see the point if both were declared, but they're not. Why is the reason?

推荐答案

如其他人所述，使用示例中的第一个表单（命名函数表达式）可以帮助调试，虽然最近浏览器中内置开发人员工具的改进，但这个论点变得不那么有说服力了。使用命名函数表达式的另一个原因是，您可以将函数名称用作函数体内的变量，而不是ES5中现在弃用的值 arguments.callee 。

As mentioned by others, using the first form in your example (a named function expression) can help with debugging, although with the recent improvements in built-in developer tools in browsers, this argument is becoming less persuasive. The other reason for using a named function expression is that you can use the function name as a variable within the body of the function rather than the now-deprecated in ES5 arguments.callee.

然而，命名函数表达式错误且在Internet Explorer中实现有问题< 9，在您定位这些浏览器时通常应该避免使用。有关详细信息，请参见 Juriy Zaytsev关于该主题的优秀文章。

However, named function expressions are incorrectly and problematically implemented in Internet Explorer < 9 and should generally be avoided when you're targeting those browsers. See Juriy Zaytsev's excellent article on the subject for more information.

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