trying to add a math.random() method to my embedded js declaration to prevent the linked javascript file from being cached.
The problem is that I keep getting syntax errors. I think I'm close but my debugging efforts are proving futile. The code is as follows:
<script type="text/javascript">
document.write("<script src='links7.js?'+Math.random()+></script>");
</script>
any suggestions?
When the HTML parser finds <script> it will start parsing the contents until it finds </script> which is present in:
document.write("<script src='links7.js?'+Math.random()+></script>
As such, you'll need to change the source so that it's not parsed as the end of a script element:
document.write("<script src='links7.js?'+Math.random()+></scri" + "pt>");
Ideally, you'd have HTML escaped all your inline JavaScript code, which would also mitigate this issue:
document.write("<script src='links7.js?'+Math.random()+></script>");
But honestly, doing that gets really annoying really quickly.
A better means of escaping all character content within your inline JavaScripts is to use a CDATA (Character Data) element:
<script type="text/javascript">
<![CDATA[
document.write("<script src='links7.js?'+Math.random()+></script>");
]]>
</script>
Of course, because the CDATA element is within the <script> element, the JS parser tries to execute it as code, and doesn't know what to do with a syntax like < ! [ CDATA [, so to get around this issue, you'll need to wrap the CDATA element in a JS comment:
<script type="text/javascript">
//<![CDATA[
-or-
/* <![CDATA[ */
//]]>
-or-
/* ]]> */
</script>
I recommend the second form, using multi-line comments so that there wont be any issues with your code if whitespace is mistakenly parsed out for whatever reasons (I've seen some Content Management Systems that drop newlines in their Rich Text Editors).
One more caveat with CDATA, the CDATA element, just like the script element, stops wrapping its contents at the first sign of its closing tag (]]>), so be careful to avoid writing something like:
lorem = ipsum[dolor[sit]]>amet;
because it will kill your CDATA element.
To avoid all of these issues, keep your JavaScripts in external .js files where they belong whenever possible.
I understand for simple one-liners it may be preferable to avoid the external file, in which case you should use the <![CDATA[ ]]> element or even HTML escape your JavaScript.
The string you've provided to document.write:
document.write("<script src='links7.js?'+Math.random()+></script>");
is incorrectly formatted to execute anything other than define a static string of <script src='link7.js?'Math.random()+></script>.
If you'd like to execute Math.random() you need to have a string before and a string after:
'<script src="links7.js?' + Math.random() + '"></script>'
You may notice that I swapped the usage of ' and ". I typically like to see " used in HTML attributes, and hate having to escape \" literals, so I use ' for string literals as often as possible in JS.
Additionally you should notice the opening and closing quote for the src attribute. The DOM may be able to give a good guess of when and where an attribute ends, but don't push it just in case it causes some breakage in your code.
</script> tags.
document.write. Make sure you're using a good text editor with syntax highlighting so that you can see when you've correctly escaped a string, and when you haven't.Step by step:
Start with what you want the code to look like:
<script src="links7.js?89736459827345"></script>
Then put it in a literal string:
'<script src="links7.js?89736459827345"></script>'
Isolate the random part in a separate string:
'<script src="links7.js?' + '89736459827345' + '"></script>'
Replace the random part with the random expression:
'<script src="links7.js?' + Math.random() + '"></script>'
Put something in the closing script tag, to keep it from messing with the script tag that it will go inside:
'<script src="links7.js?' + Math.random() + '"></scr' + 'ipt>'
Put it in a document.write call:
document.write('<script src="links7.js?' + Math.random() + '"></scr' + 'ipt>');
And the script tag around it:
<script type="text/javascript">
document.write('<script src="links7.js?' + Math.random() + '"></scr' + 'ipt>');
</script>
You've got an issue with open/close quotes. Try:
document.write("<script src='links7.js?" + Math.random() + "'></script>");
<script type="text/javascript">
document.write("<script src='links7.js?" + Math.random() + "'></script>");
</script>
Suggestion: use IDE with code highlighting.
