using document.write to write a script tag

[traq]

Hi,

I need to check if jQuery is loaded on a page, and (if not) write a script tag to load it. I found this suggestion by John Resig:

<script>
if(typeof jQuery === "undefined"){
	document.write('<script src="local/jquery.js"></script>');
}
</script>

makes sense. And, looking at the discussion, it seems that it works for others.

However, when I run it, I get this as the page output:

");

and a javascript error

unterminated string literal

it seems that the </script> tag - inside the literal string - is being treated as an actual closing script tag, instead of as a string. I've tried switching around double- and single-quotes, to no avail. Any suggestions?

[fileserverdirect]

Try escaping the characters ala: \<\/\s\c\r\i\p\t\>. Not sure if it work work, but it's worth a shot. If that doesn't work you could use <![CDATA or even "</scr"+"ipt>"

[traq]

hmm... this works

<script>
if(typeof jQuery === "undefined"){
	document.write("<script src='local/jquery.js'></"+"script>")
}
</script>

but I think it's stupid. Shouldn't the original version work?

Edit: Thought of that while you were typing. I'm trying the <![CDATA[ ]]> idea now

Edit: ...and now I'm getting ") } ]]> ...

[fileserverdirect]

hmm... this works

<script>
if(typeof jQuery === "undefined"){
	document.write("<script src='local/jquery.js'></"+"script>")
}
</script>

but I think it's stupid. Shouldn't the original version work?

No, it shouldn't because the page you are on is rendering HTML, technically anything between <script> </script> is sent for javascript processing. HTML does not know, care, or give a damn if your in a string. Thats why CDATA was invented, and the famous //<!--...

Edit:

...and now I'm getting ") } ]]> ...

try replacing </script> with <\/script>. However NORTON hates that and messes this up. PLEASE SEE THIS THREAD

[traq]

I suppose that's it, then. good resource, thanks

Edit: here's more:

<script type="text/javascript">
<!--//--><![CDATA[//><!--

//JavaScript goes here

//--><!]]>
</script>

sheesh...