函数声明后我们需要一个分号吗？ [重复]

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JavaScript: When should I use a semicolon after curly braces?

可能重复：JavaScript：花括号后我应该何时使用分号？

Someone added semicolon after function declaration, but someone not. Is this a good practice to add semicolon after function declaration?

有人在函数声明后添加了分号，但有人没有。这是在函数声明后添加分号的好习惯吗？

function test(o) {
}

function test(o) {
};

6 个解决方案

#1

A function declaration does not need (and should not have) a semicolon following it:

函数声明不需要（也不应该有）分号后面的分号：

function test(o) {
}

However, if you write a function as a statement, like the variable initializer below, then the statement should be terminated with a semicolon, just like any other statement would be:

但是，如果将函数编写为语句（如下面的变量初始化程序），则语句应以分号结束，就像任何其他语句一样：

var a = function test(o) {
};

#2

What's actually happening there is you're adding an empty statement after the function.

实际发生的是你在函数后添加一个空语句。

function test (o) { return o; };

could be seen as being similar to:

可以被视为类似于：

var test = 0;;

That second semicolon isn't an error per-se. The browser treats it like a statement where absolutely nothing happened.

第二个分号不是错误本身。浏览器将其视为一个绝对没有发生任何事情的声明。

There are two things to keep in mind, here.

这里要记住两件事。

This applies ONLY to function-declarations and control-blocks (for/if/while/switch/etc).

这仅适用于函数声明和控制块（对于/ if / while / switch / etc）。

Function-declarations should be defined at the bottom of your scope, so you don't run into problems like this:

函数声明应该在作用域的底部定义，所以你不会遇到这样的问题：

function test () {}
(function (window, document, undefined) { /* do stuff */ }(window, document));

Because the browser will assume that you mean function test() {}(/*return value of closure*/); Which is an error. A very bad and nasty error which is very easy to overlook.

因为浏览器会假设你的意思是函数test（）{}（/ *返回值* /）;这是一个错误。一个非常糟糕和令人讨厌的错误很容易被忽视。

But that's okay, because function-declarations can go under return statements and still work just fine.

但是没关系，因为函数声明可以在返回语句下进行，但仍然可以正常工作。

So even if you wanted to go:

所以，即使你想去：

function doStuff () {
    return (function () { /*process stuff*/ test(); }());
    function test () {}
}

That's going to work just peachy.

这只会起作用。

#3

No.

没有。

You don't need semicolons when defining a function like that.

定义像这样的函数时，不需要分号。

However, if you define a function like this:

但是，如果您定义这样的函数：

var test = function (o) {
}

It's not strictly necessary, but you may want to use them, especially if you put the function on one line.

这不是绝对必要的，但您可能想要使用它们，特别是如果您将功能放在一行上。

The first way defines a function, but the second way assigns a function to a variable, and thus is a statement. Most statements are semicolon delimited. Defining functions could be considered a common counterexample, as not many people do use them.

第一种方式定义了一个函数，但第二种方式是将函数赋给变量，因此是一个语句。大多数语句都以分号分隔。定义函数可以被认为是一个常见的反例，因为没有多少人使用它们。

#4

Semicolons and function declarations:

分号和函数声明：

function test(o) {
    // body
} // semicolon no

var test = function (o) {
    // body
}; // semicolon yes

See JSLint for formatting code questions.

请参阅JSLint以格式化代码问题。

#5

To the browser, it doesn't matter. For matter of semantics, it only matters if you're prototyping a function or using the function statement.

对浏览器来说，没关系。对于语义问题，只有在对函数进行原型设计或使用函数语句时才有意义。

function stuff(stuff) {
     alert(stuff);
} //don't need a semicolon

Object.prototype.stuff = function(stuff) {
    alert(stuff);
}; //need a semicolon
var stuff = function(stuff) {
    alert(stuff);
}; //need a semicolon

#6

Semicolon is not required while defining a function, but putting it on is not a mistake either.

定义函数时不需要分号，但是打开它也不是错误。

One exception though, if you use function wrappers and pass the parameters, you need to add semicolons in between, example:

但有一个例外，如果你使用函数包装器并传递参数，你需要在它们之间添加分号，例如：

(function(v){alert(v)})('1');
(function(s){alert(s)})('0')

or it will result in error: http://jsfiddle.net/twUD3/1/
或者它会导致错误：http：//jsfiddle.net/twUD3/1/

... Otherwise forget about them ...

......别忘了他们......

#1