Pass vars to JavaScript via the SRC attribute

Question

In my HTML file I have linked to the JS with:

src="myscript.js?config=true"

Can my JS directly read the value of this var like this?

alert (config);

This does not work, and the FireFox Error Console says "config is not defined". How do I read the vars passed via the src attribute in the JS file? Is it this simple?

Answer 1

<script>
var config=true;
</script>
<script src="myscript.js"></script>

You can't pass variables to JS the way you tried. SCRIPT tag does not create a Window object (which has a query string), and it is not server side code.

Answer 2

You might have seen this done, but really the JS file is being preprocessed server side using PHP or some other language first. The server side code will print/echo the javascript with the variables set. I've seen a scripted ad service do this before, and it made me look into seeing if it can be done with plain ol' js, but it can't.

Answer 3

Yes, you can, but you need to know the exact script file name in the script :

var libFileName = 'myscript.js',
    scripts = document.head.getElementsByTagName("script"), 
    i, j, src, parts, basePath, options = {};

for (i = 0; i < scripts.length; i++) {
  src = scripts[i].src;
  if (src.indexOf(libFileName) != -1) {
    parts = src.split('?');
    basePath = parts[0].replace(libFileName, '');
    if (parts[1]) {
      var opt = parts[1].split('&');
      for (j = opt.length-1; j >= 0; --j) {
        var pair = opt[j].split('=');
        options[pair[0]] = pair[1];
      }
    }
    break;
  }
}

You have now an 'options' variable which has the arguments passed. I didn't test it, I changed it a little from http://code.google.com/p/canvas-text/source/browse/trunk/canvas.text.js where it works.

Answer 4

You need to use Javascript to find the src attribute of the script and parse the variables after the '?'. Using the Prototype.js framework, it looks something like this:

var js = /myscript\.js(\?.*)?$/; // regex to match .js

var jsfile = $$('head script[src]').findAll(function(s) {
    return s.src.match(js);
}).each(function(s) {
    var path = s.src.replace(js, ''),
    includes = s.src.match(/\?.*([a-z,]*)/);
    config = (includes ? includes[1].split('=');
    alert(config[1]); // should alert "true" ??
});

My Javascript/RegEx skills are rusty, but that's the general idea. Ripped straight from the scriptaculous.js file!

Answer 5

Your script can however locate its own script node and examine the src attribute and extract whatever information you like.

  var scripts = document.getElementsByTagName ('script');
  for (var s, i = scripts.length; i && (s = scripts[--i]);) {
    if ((s = s.getAttribute ('src')) && (s = s.match (/^(.*)myscript.js(\?\s*(.+))?\s*/))) {
      alert ("Parameter string : '" + s[3] + "'");    
      break;
    } 
  }