HTML中script元素的charset属性的目的是什么？

Question

In HTML, script element has optional charset attribute.

What is the purpose of it?

When is it useful?

Answer 1

If your javascript files are encoded with a different encoding than the page is using, you can use the charset attribute to tell the browser how to interpret it.

For example, if the page is using Latin1 , but the JS file was created with UTF-8 .

Answer 2

The purpose of the charset parameter is to specify the encoding of the external script in cases where the encoding is not specified at the HTTP protocol level. It is not meant to override encoding information in HTTP headers, and it does not do that.

This is useful when the author cannot control HTTP headers and the headers do not specify character encoding. It is also useful for offline files, such as in a local copy of a web page accessed directly, not via an HTTP server, so that no HTTP headers exist.

In practice, it is not very useful. If you need to use non-Ascii characters in a JavaScript file, you can use UTF-8 encoding. If you use UTF-8 with a leading BOM, the BOM acts as a useful indicator that lets browsers infer the encoding. But it does not hurt to additionally use charset=utf-8 .

Answer 3

Each JavaScript file is a separate element from page, after all you can even load JS from some remote author's server that otherwise have no relations to your page at all. Just as with any other external element, you can manually specify "charset" if remote server returns wrong charset for some reason or just to be sure.

Also, if you have write access to this JS file yourself, you may want to replace all non-ASCII with Unicode position escapes - this will guarantee that symbols will always be interpreted correctly, no matter what encoding is specified in headers. Some JS minifiers, like Google Closure Compiler, can do it for you automatically.