blocks|key|1182187|text|用于调试目的。如果您使用命名函数，则可以在您喜欢的开发工具的调用堆栈跟踪中看到该名称。否则你会看到anonymous+function。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1182188|entityMap^0|1D|I|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

For debugging purposes. If you use a named function you can see that name in the call stack trace in your favorite dev tools. Otherwise you'd see <code>anonymous function</code>.

blocks|key|38371|text|这就是所谓的named+function+expression+(或NFE)，它使调试过程变得更加容易。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|38372|38373|需要记住的一个重要细节是，此名称仅在新定义的函数的作用域中可用；specs要求标识符不应在封闭的作用域中可用：|blockquote|38374|38375|38376|var+f+=+function+foo(){
++return+typeof+foo;+//+"foo"+is+available+in+this+inner+scope
};
//+`foo`+is+never+visible+"outside"
typeof+foo;+//+"undefined"
f();+//+"function"|code-block|syntax|javascript|38377|entityMap|0|LINK|mutability|MUTABLE|url|http://kangax.github.io/nfe/^0|6|P|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|-4|5|6|7|10|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|11|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|12|8|@]|9|@]|C|$]]|$1|I|3|-4|5|6|7|13|8|@]|9|@]|C|$]]|$1|J|3|K|5|L|7|14|8|@]|9|@]|C|$M|N]]|$1|O|3|-4|5|6|7|15|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]]]

That's called a <a href="http://kangax.github.io/nfe/" rel="nofollow">named function expression</a> (or NFE) and it makes the debugging process much easier.

<blockquote>
 An important detail to remember is that this name is only available in
 the scope of a newly-defined function; specs mandate that an
 identifier should not be available to an enclosing scope:
</blockquote>

<pre><code>var f = function foo(){
 return typeof foo; // "foo" is available in this inner scope
};
// `foo` is never visible "outside"
typeof foo; // "undefined"
f(); // "function"
</code></pre>

blocks|key|2836220|text|正如其他人所说，主要是为了调试目的。但不仅如此。例如，您可以依赖这样一个事实，即在函数体中，您可以使用您设置的名称访问函数本身。举个愚蠢的例子：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2836221|var+sum+=+function+(a,+b)+{
++++if+(a+<+3)
++++++++return+sum(3+%2B+a,+b);

++++return+a+%2B+b;
}

sum(1,+2)+//+3;|code-block|syntax|javascript|2836222|但让我们看看现在会发生什么：|2836223|var+aSum+=+sum;
sum+=+null;

aSum(1,+3);+//+TypeError:+sum+is+not+a+function|2836224|命名函数，将涵盖该用例：|2836225|var+sum+=+function+sum(a,+b)+{
++++if+(a+<+3)
++++++++return+sum(3+%2B+a,+b);

++++return+a+%2B+b;
}

sum(1,+2)+//+6

var+aSum+=+sum;
sum+=+null;

aSum(1,+2)+//+6|2836226|这是因为在函数体中，函数的名称总是引用它，而不是像第一个示例那样从另一个作用域获取。|2836227|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

As others says, for debugging purposes mainly. But not only that. For instance, you can rely on the fact that in function's body, you can access to the function itself using the name you set. To give a silly example:

<pre><code>var sum = function (a, b) {
 if (a &lt; 3)
 return sum(3 + a, b);

 return a + b;
}

sum(1, 2) // 3;
</code></pre>

But let's see what happens now:

<pre><code>var aSum = sum;
sum = null;

aSum(1, 3); // TypeError: sum is not a function
</code></pre>

Naming the function, will cover that use case:

<pre><code>var sum = function sum(a, b) {
 if (a &lt; 3)
 return sum(3 + a, b);

 return a + b;
}

sum(1, 2) // 6

var aSum = sum;
sum = null;

aSum(1, 2) // 6
</code></pre>

That's because in the body of the function, the name of the function is always referring to it, and is not taken from another scope, like the first example.

I recently came across this pattern in the source for <a href="https://github.com/yeoman/generator-webapp" rel="noreferrer">https://github.com/yeoman/generator-webapp</a>:

<pre><code>AppGenerator.prototype.packageJSON = function packageJSON() {
 this.template('_package.json', 'package.json');
};
</code></pre>

What's the purpose of giving the function the name "packageJSON" when you're going to assign it to a variable or object property anyways? I've always used anonymous functions in similar cases.

What is the purpose using a named function when assigning to a variable in JavaScript?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我最近在的源代码中遇到了这个模式AppGenerator.prototype.packageJSON = function packageJSON() {  this.template('_package.json', 'package.json');};当你要将函数赋值给一个变量或对象属性时，给它命名为"packag...

问在JavaScript中为变量赋值时，使用命名函数的目的是什么？
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问在JavaScript中为变量赋值时，使用命名函数的目的是什么？EN