How to pass parameters to a Script tag?

Got it. Kind of a hack, but it works pretty nice:

var params = document.body.getElementsByTagName('script');
query = params[0].classList;
var param_a = query[0];
var param_b = query[1];
var param_c = query[2];

I pass the params in the script tag as classes:

<script src="http://path.to/widget.js" class="2 5 4"></script>

This article helped a lot.

It's better to Use feature in html5 5 data Attributes

<script src="http://path.to/widget.js" data-width="200" data-height="200">
</script>

Inside the script file http://path.to/widget.js you can get the paremeters in that way:

<script>
function getSyncScriptParams() {
         var scripts = document.getElementsByTagName('script');
         var lastScript = scripts[scripts.length-1];
         var scriptName = lastScript;
         return {
             width : scriptName.getAttribute('data-width'),
             height : scriptName.getAttribute('data-height')
         };
 }
</script>

I apologise for replying to a super old question but after spending an hour wrestling with the above solutions I opted for simpler stuff.

<script src=".." one="1" two="2"></script>

Inside above script:

document.currentScript.getAttribute('one'); //1
document.currentScript.getAttribute('two'); //2

Much easier than jquery OR url parsing.

You might need the polyfil for doucment.currentScript from @Yared Rodriguez's answer for IE:

document.currentScript = document.currentScript || (function() {
  var scripts = document.getElementsByTagName('script');
  return scripts[scripts.length - 1];
})();

Another way is to use meta tags. Whatever data is supposed to be passed to your JavaScript can be assigned like this:

<meta name="yourdata" content="whatever" />
<meta name="moredata" content="more of this" />

The data can then be pulled from the meta tags like this (best done in a DOMContentLoaded event handler):

var data1 = document.getElementsByName('yourdata')[0].content;
var data2 = document.getElementsByName('moredata')[0].content;

Absolutely no hassle with jQuery or the likes, no hacks and workarounds necessary, and works with any HTML version that supports meta tags...