javascript注释_JavaScript注释

javascript注释

As with HTML & CSS, it is good practice to comment your code: not only for yourself, but also for anyone who might come after you. Comments also have other uses in development, which I’ll explain at the end of this article.

与HTML和CSS一样，注释代码是一个好习惯：不仅对您自己，而且对任何可能追随您的人也是如此。注释在开发中还有其他用途，我将在本文结尾处进行解释。

单行JavaScript注释 (Single-Line JavaScript Comments)

Any text or code on a single line can be turned into a comment by preceding it with two forward slashes:

一行上的任何文本或代码都可以在其前面加上两个正斜杠来变成注释：

// this is a single-line comment

While this works well for brief descriptions or to comment out one line of non-functional code, it doesn’t provide the space needed for longer explanations. In addition, there is a small risk that a long single-line comment will accidentally catch an errant carriage return and accidentally break over two lines. If that happens, the second uncommented line will cause a syntax error.

尽管这对于简短的描述或注释掉一行非功能性代码非常有效，但它并没有提供较长的解释所需的空间。此外，单行较长的注释可能会误捕获错误的回车符并意外中断两行。如果发生这种情况，第二条未注释的行将导致语法错误。

多行JavaScript注释 (Multi-Line JavaScript Comments)

Multi-line comments in JavaScript are exactly the same as those in CSS:

JavaScript中的多行注释与CSS中的注释完全相同：

/* this is a
multi-line comment */

Multi-line comments are obviously much more flexible than the single line version.

多行注释显然比单行版本更灵活。

在开发中使用注释 (Using Comments In Development)

Comments are not only useful for leaving notes and reminders, but for temporarily removing problematic code from execution:

注释不仅对留下注释和提醒有用，而且对于从执行中临时删除有问题的代码也非常有用：

function pill(dose) {
bottle++;
// gulp++; this commented line will not be executed
}

This can be very useful, but of course you must be careful in only commenting out code that you don’t want to run.

这是非常有用的，当然你必须只注释掉的代码，你不希望运行小心。

IE奇数：条件编译 (IE Oddities: Conditional Compilation)

Like HTML conditional comments, Internet Explorer version 10 and below (and only IE) will run code in JavaScript comments if the comment starts with a /*@cc_on @*/ statement. This can be used to target earlier versions of IE with JavaScript without affecting other browsers. More information on conditional compilation can be found at the Microsoft Internet Explorer Dev Center.

与HTML条件注释一样，如果注释以/*@cc_on @*/开头，则Internet Explorer 10及更低版本( 仅 IE)将在JavaScript注释中运行代码。这可以用于使用JavaScript定位IE的早期版本，而不会影响其他浏览器。有关条件编译的更多信息，请访问Microsoft Internet Explorer开发中心。

删除生产注释 (Removing Comments For Production)

It’s a good and common practice to strip comments, whitespace and any unused code from scripts before deploying them on a live site, to minimize file size and load time. Tools such as Uglify.js can do this automatically in a build process; alternatively, an online JS minifier can be employed. Of course, it’s vital to preserve the original fully formatted and commented code for future work.

在脚本中删除注释，空格和任何未使用的代码，然后再将它们部署到实时站点上是一个好习惯，这是最小化文件大小和加载时间的最佳做法。诸如Uglify.js之类的工具可以在构建过程中自动执行此操作。或者，可以使用在线JS缩小器。当然，保留原始的完整格式和注释代码对于以后的工作至关重要。

“如果我想在精简的JS代码中保留一些注释怎么办？” (“What If I Want To Preserve Some Comments In Minified JS Code?”)

In certain cases you might want to preserve some comments in your scripts, such as those containing copyright claims, developer credits and licensing information, while removing all others. Many minifiers will preserve JS comments if they contain one of two character strings:

string	meaning
`@preserve`	general preservation rule for comments
`@license`	a comment that contains licensing information

串	含义
`@preserve`	通用注释保存规则
`@license`	包含许可信息的评论

So a comment that included the following:

因此，一条评论包括以下内容：

/* @preserve
A shoutout to all my West Side homies. Nerds4Lyfe.
*/

Would be retained as a comment (sans the @preserve keyword) in the minified, production version of the JavaScript code.

将在JavaScript代码的@preserve生产版本中保留为注释( 不带@preserve关键字)。

翻译自: https://thenewcode.com/932/JavaScript-Comments

javascript注释