在 JavaScript 开头以分号开头的目的是什么？
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What's the purpose of starting semi colon at beginning of JavaScript?
提问by benpalmer
Possible Duplicate:
What does the leading semicolon in JavaScript libraries do?
可能的重复：
JavaScript 库中的前导分号有什么作用？
I have noticed a lot of jQuery plugins start with
我注意到很多 jQuery 插件都是以
;(function(){ /* something in here */ })();
I just wondered what the beginning semi-colon was for, as well as the empty parentheses at the end.
我只是想知道开头的分号是什么，以及末尾的空括号是什么。
回答by James Gaunt
The semi-colon is there in case you include this script just after some 'bad' script that doesn't properly close off its last line with a semi-colon. In this case it's possible the two scripts would be combined and result in invalid code. For example if you are merging multiple script into a single response.
分号在那里，以防您在一些“坏”脚本之后包含此脚本，这些脚本没有用分号正确关闭其最后一行。在这种情况下，这两个脚本可能会组合在一起并导致无效代码。例如，如果您将多个脚本合并为一个响应。
The () at the end is executing the function. This is creating a closure. Private variables and methods can be declared within the scope of this function that cannot be accessed from outside the script.
最后的 () 正在执行函数。这是在创建一个闭包。私有变量和方法可以在这个函数的范围内声明，不能从脚本外部访问。
回答by slaphappy
This construct :
这个构造：
(function(){ /* something in here */ })()
Is used to create a new scope in Javascript.
用于在 Javascript 中创建新范围。
More info on function scope here.
Regarding the semicolon, I never seen it before. I think it's a security for when you concatenate several scripts, since semicolons are optional in some cases at the end of the file.
关于分号，我以前从未见过。我认为这是连接多个脚本时的安全性，因为在某些情况下，分号在文件末尾是可选的。
