Why are javascripts sometimes surrounded by these tags?
Why are some JavaScripts encapsulated within these tags:
<!--//--><![CDATA[//>开发者_运维问答<!--
some js here
//--><!]]>
<![CDATA[//>
is to prevent XML parsers from choking on the script.
<!-- ... -->
is not required unless you're using Netscape 1.0.
See: Does it still make sense to use HTML comments on blocks of JavaScript?
It makes it valid XHTML.
They were used for old browsers which didn't understand the <script>
tag. That way if a browser didn't properly read the JavaScript, it would just render it as a comment and not show up on the page.
It also allows JavaScript code to be inside valid XHTML pages without having to escape characters which aren't valid in XML.
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