JavaScript Script Tags

The HTML script tag is used to identify and run javaScript code.

  • The browser reads each script tag in the order in which it appears in the document.
  • The javascript defined by a script tag is compiled and run immediately after the tag is recognized by the browser.
  • There is no limit to the number of script tags in a document.
  • The same-origin policy prevents scripts hosted at other domains from running unless CORS has been setup.

NOTE: For older code:

  • type="text/javascript" is required in the script tag in HTML 4 and XHTML, but optional in HTML5.
  • CDATA is needed for XHTML pages if the script has any HTML characters like < and > in it. <script>//<![CDATA[ ...code... //]]></script>
  • Do not use the <!-- //--> hack with scripts. It was intended to prevent scripts from showing up as text on the first generation browsers Netscape 1 and Mosaic.


<script name="my_script" src="path/or/url/to/my_script.js"></script>
  • When referencing a file, no javascript code should be put inside the tag.
  • The name attribute is optional and is intended for humans only.


<script>/* JavaScript code here */</script>


script tags can be dynamically created from running JavaScript.

    document.write('\x3Cscript' + 'src="my_other_script.js">\x3C/script>');