javascript - 服务器设置了mime类型，为什么要写<script type ="text/javascript">？

Question

我的理解是 mime 类型是由网络服务器设置的。为什么我们要添加type="text/javascript 或type="text/css" 属性？这不是无用且被忽略的属性吗？

Answer 1

Douglas Crockford says :

type="text/javascript"

This attribute is optional. Since Netscape 2, the default programming language in all browsers has been JavaScript. In XHTML, this attribute is required and unnecessary. In HTML, it is better to leave it out. The browser knows what to do.

He also says:

W3C did not adopt the language attribute, favoring instead a type attribute which takes a MIME type. Unfortunately, the MIME type was not standardized, so it is sometimes "text/javascript" or "application/ecmascript" or something else. Fortunately, all browsers will always choose JavaScript as the default programming language, so it is always best to simply write <script>. It is smallest, and it works on the most browsers.

仅供娱乐，我尝试了以下五个脚本

  <script type="application/ecmascript">alert("1");</script>
  <script type="text/javascript">alert("2");</script>
  <script type="baloney">alert("3");</script>
  <script type="">alert("4");</script>
  <script >alert("5");</script>

在 Chrome 上，除了脚本 3 ( type="baloney" ) 之外的所有脚本都有效。 IE8 没有运行脚本 1 ( type="application/ecmascript" ) 或脚本 3。根据我对两个浏览器的非广泛示例，看起来您可以放心地忽略 type。属性，但如果你使用它，你最好使用一个合法的(依赖于浏​​览器的)值。