var functionName = 函数() {} vs 函数函数Name() {}

我最近开始保持别人的JavaScript代码,我正在修复错误,添加功能,也试图更新代码并使其更加一致。

以前的开发人员使用了两种方式来宣布功能,我无法解决是否有原因。

兩種方式是:

var functionOne = function() {
    // Some code
};

function functionTwo() {
    // Some code
}

使用这两种不同的方法的原因是什么?每个方法的优点和缺点是什么?可以用一种方法做些什么,不能用另一种方法做些什么?

当前回答

第一個例子是一個功能宣言:

function abc(){}

第二个例子是函数表达:

var abc = function() {};

在第一個例子中,整個函數宣言都被封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封封。

把它简单地说:

//this will work
abc(param);
function abc(){}

//this would fail
abc(param);
var abc = function() {}

要了解更多关于这个主题,我强烈推荐这个链接。

2014-06-05 08:28:44

其他回答

新函数()可以用来将函数的身体转移到一条线上,因此可以用来创建动态函数,也可以通过脚本而不执行脚本。

var func = new Function("x", "y", "return x*y;");
function secondFunction(){
   var result;
   result = func(10,20);
   console.log ( result );
}

secondFunction()

2016-05-10 07:05:46

尝试 { console.log(“成功:”,添加(1, 1)); } 捕捉(e) { console.log(“错误:” + e); } var add=function(a, b){ return a + b; }

2021-10-21 12:33:27

鉴于“名称函数在轨道上出现”的论点,现代的JavaScript引擎实际上非常能够代表匿名函数。

至于这篇文章,V8,SpiderMonkey,Chakra和Nitro总是提到他们的名字命名的函数,他们几乎总是提到一个匿名函数,它的识别器,如果它有一个。

SpiderMonkey 可以从另一个函数返回的匿名函数的名称。

如果你真的,真的想要你的 iterator 和成功的呼叫回复出现在轨道上,你可以命名那些也。

[].forEach(function iterator() {});

但是,大多数情况下,它不值得强调。

哈里斯(Fiddle)

'use strict';

var a = function () {
    throw new Error();
},
    b = function b() {
        throw new Error();
    },
    c = function d() {
        throw new Error();
    },
    e = {
        f: a,
        g: b,
        h: c,
        i: function () {
            throw new Error();
        },
        j: function j() {
            throw new Error();
        },
        k: function l() {
            throw new Error();
        }
    },
    m = (function () {
        return function () {
            throw new Error();
        };
    }()),
    n = (function () {
        return function n() {
            throw new Error();
        };
    }()),
    o = (function () {
        return function p() {
            throw new Error();
        };
    }());

console.log([a, b, c].concat(Object.keys(e).reduce(function (values, key) {
    return values.concat(e[key]);
}, [])).concat([m, n, o]).reduce(function (logs, func) {

    try {
        func();
    } catch (error) {
        return logs.concat('func.name: ' + func.name + '\n' +
                           'Trace:\n' +
                           error.stack);
        // Need to manually log the error object in Nitro.
    }

}, []).join('\n\n'));

func.name: 
Trace:
Error
    at a (http://localhost:8000/test.js:4:11)
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27

func.name: b
Trace:
Error
    at b (http://localhost:8000/test.js:7:15)
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27

func.name: d
Trace:
Error
    at d (http://localhost:8000/test.js:10:15)
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27

func.name: 
Trace:
Error
    at a (http://localhost:8000/test.js:4:11)
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27

func.name: b
Trace:
Error
    at b (http://localhost:8000/test.js:7:15)
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27

func.name: d
Trace:
Error
    at d (http://localhost:8000/test.js:10:15)
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27

func.name: 
Trace:
Error
    at e.i (http://localhost:8000/test.js:17:19)
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27

func.name: j
Trace:
Error
    at j (http://localhost:8000/test.js:20:19)
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27

func.name: l
Trace:
Error
    at l (http://localhost:8000/test.js:23:19)
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27

func.name: 
Trace:
Error
    at http://localhost:8000/test.js:28:19
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27

func.name: n
Trace:
Error
    at n (http://localhost:8000/test.js:33:19)
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27

func.name: p
Trace:
Error
    at p (http://localhost:8000/test.js:38:19)
    at http://localhost:8000/test.js:47:9
    at Array.reduce (native)
    at http://localhost:8000/test.js:44:27 test.js:42

蜘蛛侠

func.name: 
Trace:
a@http://localhost:8000/test.js:4:5
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1


func.name: b
Trace:
b@http://localhost:8000/test.js:7:9
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1


func.name: d
Trace:
d@http://localhost:8000/test.js:10:9
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1


func.name: 
Trace:
a@http://localhost:8000/test.js:4:5
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1


func.name: b
Trace:
b@http://localhost:8000/test.js:7:9
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1


func.name: d
Trace:
d@http://localhost:8000/test.js:10:9
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1


func.name: 
Trace:
e.i@http://localhost:8000/test.js:17:13
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1


func.name: j
Trace:
j@http://localhost:8000/test.js:20:13
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1


func.name: l
Trace:
l@http://localhost:8000/test.js:23:13
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1


func.name: 
Trace:
m</<@http://localhost:8000/test.js:28:13
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1


func.name: n
Trace:
n@http://localhost:8000/test.js:33:13
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1


func.name: p
Trace:
p@http://localhost:8000/test.js:38:13
@http://localhost:8000/test.js:47:9
@http://localhost:8000/test.js:54:1

查克拉

func.name: undefined
Trace:
Error
   at a (http://localhost:8000/test.js:4:5)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)


func.name: undefined
Trace:
Error
   at b (http://localhost:8000/test.js:7:9)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)


func.name: undefined
Trace:
Error
   at d (http://localhost:8000/test.js:10:9)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)


func.name: undefined
Trace:
Error
   at a (http://localhost:8000/test.js:4:5)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)


func.name: undefined
Trace:
Error
   at b (http://localhost:8000/test.js:7:9)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)


func.name: undefined
Trace:
Error
   at d (http://localhost:8000/test.js:10:9)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)


func.name: undefined
Trace:
Error
   at e.i (http://localhost:8000/test.js:17:13)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)


func.name: undefined
Trace:
Error
   at j (http://localhost:8000/test.js:20:13)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)


func.name: undefined
Trace:
Error
   at l (http://localhost:8000/test.js:23:13)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)


func.name: undefined
Trace:
Error
   at Anonymous function (http://localhost:8000/test.js:28:13)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)


func.name: undefined
Trace:
Error
   at n (http://localhost:8000/test.js:33:13)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)


func.name: undefined
Trace:
Error
   at p (http://localhost:8000/test.js:38:13)
   at Anonymous function (http://localhost:8000/test.js:47:9)
   at Global code (http://localhost:8000/test.js:42:1)

尼特

func.name: 
Trace:
a@http://localhost:8000/test.js:4:22
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

func.name: b
Trace:
b@http://localhost:8000/test.js:7:26
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

func.name: d
Trace:
d@http://localhost:8000/test.js:10:26
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

func.name: 
Trace:
a@http://localhost:8000/test.js:4:22
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

func.name: b
Trace:
b@http://localhost:8000/test.js:7:26
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

func.name: d
Trace:
d@http://localhost:8000/test.js:10:26
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

func.name: 
Trace:
i@http://localhost:8000/test.js:17:30
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

func.name: j
Trace:
j@http://localhost:8000/test.js:20:30
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

func.name: l
Trace:
l@http://localhost:8000/test.js:23:30
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

func.name: 
Trace:
http://localhost:8000/test.js:28:30
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

func.name: n
Trace:
n@http://localhost:8000/test.js:33:30
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

func.name: p
Trace:
p@http://localhost:8000/test.js:38:30
http://localhost:8000/test.js:47:13
reduce@[native code]
global code@http://localhost:8000/test.js:44:33

2014-10-12 00:58:57

要注意的一个重要点是:

让我们有两个功能:

sum(1,2);

const sum = function(first, second) {
  return first + second;
}

在上述情況下,它會導致錯誤,金額不被定義,但

sum(1,2);

function sum(first, second) {
  return first + second;
}

此函数不会有任何错误,因为在这种情况下会发生 Hoisting。

2018-10-18 18:57:07

你在那里发布的两个代码剪辑,几乎所有目的都会以相同的方式行事。

然而,行为的差异是,在第一个变量(有函数One = 函数() {}),该函数只能在代码中的那个点之后被称为。

第二个选项(函数Two()),函数可用于代码,运行在函数被宣布的地方。

这是因为第一种变量,函数在运行时分配给变量foo;第二种函数在运行时分配给这个识别器,foo。

更多技术信息

JavaScript 有三种方式来定义功能。

你的第一个剪辑显示一个函数表达式. 这意味着使用“函数”操作员创建一个函数 - 该操作员的结果可以存储在任何变量或对象属性. 函数表达式是强大的这种方式. 函数表达式经常被称为“匿名函数”,因为它不需要一个名字, 你的第二个例子是一个函数声明。

2010-04-20 04:54:49

var functionName = 函数() {} vs 函数函数Name() {}

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