Detailed explanation of the usage of JavaScript in XHTML_Basic knowledge

The rules for writing XHTML code are much stricter than writing HTML. Code like the following is valid in HTML, but invalid in XHTML.
[javascript]

Copy code The code is as follows:

In HTML, there are special rules to determine what content in the <script> element can be parsed, but these rules do not apply in XHTML. Because the less than sign (<) will be parsed as starting a new tag in XHTML. However, as a label, the less than sign cannot be followed by a space, thus causing a syntax error. <BR>There are two solutions: first, replace all less than signs (<) in the code with the corresponding HTML entities (<); second, use a CData fragment to contain the JavaScript code. <BR>Corresponding code for method one: <BR>[javascript] <BR><div class="codetitle"><span><a style="CURSOR: pointer" data="41685" class="copybut" id="copybut41685" onclick="doCopy('code41685')"><U>Copy code The code is as follows: <div class="codebody" id="code41685"> <BR><script type="text/javascript"> <BR>function compare(a, b) <BR>{ <BR>if(a < b) <BR>{ <BR>alert("a is less then b"); <BR>} <BR>else if(a > b) <BR>{ <BR>alert("a is greater then b"); <BR>} <BR>else <BR> { <BR>alert("a is equal to b"); <BR>} <BR>} <BR></script>


Corresponding code for method two:
[javascript]

Copy code The code is as follows:

Although method one can make the code run normally in XHTML, it makes the code difficult to understand; while method two can solve the problem in XHTML-compatible browsers. However, many browsers are not compatible with XHTML and therefore do not support CData fragments. So use JavaScript comments to comment out the CData tag.
Corresponding code:
[html]

Copy code The code is as follows:

> ;

This format works well in all modern browsers.
Attachment: Deprecated syntax
[javascript]

Copy code The code is as follows:

<script><!-- <BR>function sayHi(){ <BR>alert("Hi!); <BR>} <BR>//--></script>> ;
<script><!-- <BR>function sayHi(){ <BR>alert("Hi!); <BR>} <BR>//--></script>

Wrapping JavaScript code in an HTML comment as above allows browsers that do not support the <script> element to hide the embedded JavaScript code, i.e. ignore the content in the <script> tag, and When browsers that support JavaScript encounter this situation, they must further confirm whether it contains JavaScript code that needs to be parsed. <br><br>Although this comment format is recognized by all browsers and can be interpreted correctly, since all browsers already support JavaScript, there is no need to use this format anymore.</script>