Reading GET variables with JavaScript

by Josh Fraser on June 10, 2009

One of the things that isn’t immediately obvious in JavaScript is how to access GET variables. I’ve seen lots of different implementations for this around the web, but the majority of them are bulkier than they need to be. Here’s my favorite way to do it:

<script type='text/javascript'>

function $_GET(q,s) {
    s = (s) ? s : window.location.search;
    var re = new RegExp('&amp;'+q+'=([^&amp;]*)','i');
    return (s=s.replace(/^\?/,'&amp;').match(re)) ?s=s[1] :s='';
}

</script>

What this gives you is a JavaScript implementation of PHP’s $_GET functionality.  I use a regular expression to keep the code to a minimum. Here is a simple example of how to use it:

// this code would print "hello world" if it was at http://localhost/index.php?var1=hello&var2=world
var var1 = $_GET('var1');
var var2 = $_GET('var2');
document.write(var1 + " " + var2);

Another thing I like about this implementation is that it makes it easy to parse GET variables from arbitrary search strings (ex “?var1=hello&var2=world”).  This is handy if you need to access GET variables from an HTML src parameter such as an image or script tag.

// get the src parameter and split it down to the search query string
var src = document.getElementById('example').src;
params = src.split('?');
var var1 = $_GET('var1','?'+params[1]);

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Comments

  1. James Printer said at 3:49 pm on September 7th, 2009:

    Thanks :)

  2. vsync said at 10:02 am on January 11th, 2010:

    your code misinterpreted this query:
    ?a=1&b=2&a=true&c=7xxx

    'a' is '1' instead of 'true'

  3. Josh Fraser said at 7:32 pm on January 11th, 2010:

    you define 'a' twice. while the regexp could obviously be altered to look for the last instance, it's better coding practice to to avoid ambiguous cases like that.

  4. personAtRandom said at 10:07 pm on February 13th, 2010:

    This is magic, as far as I'm concerned, so I can't diagnose this, but the function only returns the GET variable up to (and not including) the first instance of the letter 'a'. Truly weird!

  5. Martin said at 5:04 pm on February 23rd, 2010:

    Does the code work with eg: example.com?a=1#chapter10

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