[javascript] Parse query string in JavaScript

Me too! http://jsfiddle.net/drzaus/8EE8k/

(Note: without fancy nested or duplicate checking)

deparam = (function(d,x,params,p,i,j) {
return function (qs) {
    // start bucket; can't cheat by setting it in scope declaration or it overwrites
    params = {};
    // remove preceding non-querystring, correct spaces, and split
    qs = qs.substring(qs.indexOf('?')+1).replace(x,' ').split('&');
    // march and parse
    for (i = qs.length; i > 0;) {
        p = qs[--i];
        // allow equals in value
        j = p.indexOf('=');
        // what if no val?
        if(j === -1) params[d(p)] = undefined;
        else params[d(p.substring(0,j))] = d(p.substring(j+1));
    }

    return params;
};//--  fn  deparam
})(decodeURIComponent, /\+/g);

And tests:

var tests = {};
tests["simple params"] = "ID=2&first=1&second=b";
tests["full url"] = "http://blah.com/?third=c&fourth=d&fifth=e";
tests['just ?'] = '?animal=bear&fruit=apple&building=Empire State Building&spaces=these+are+pluses';
tests['with equals'] = 'foo=bar&baz=quux&equals=with=extra=equals&grault=garply';
tests['no value'] = 'foo=bar&baz=&qux=quux';
tests['value omit'] = 'foo=bar&baz&qux=quux';

var $output = document.getElementById('output');
function output(msg) {
    msg = Array.prototype.slice.call(arguments, 0).join("\n");
    if($output) $output.innerHTML += "\n" + msg + "\n";
    else console.log(msg);
}
var results = {}; // save results, so we can confirm we're not incorrectly referencing
$.each(tests, function(msg, test) {
    var q = deparam(test);
    results[msg] = q;
    output(msg, test, JSON.stringify(q), $.param(q));
    output('-------------------');
});

output('=== confirming results non-overwrite ===');
$.each(results, function(msg, result) {
    output(msg, JSON.stringify(result));
    output('-------------------');
});

Results in:

simple params
ID=2&first=1&second=b
{"second":"b","first":"1","ID":"2"}
second=b&first=1&ID=2
-------------------
full url
http://blah.com/?third=c&fourth=d&fifth=e
{"fifth":"e","fourth":"d","third":"c"}
fifth=e&fourth=d&third=c
-------------------
just ?
?animal=bear&fruit=apple&building=Empire State Building&spaces=these+are+pluses
{"spaces":"these are pluses","building":"Empire State Building","fruit":"apple","animal":"bear"}
spaces=these%20are%20pluses&building=Empire%20State%20Building&fruit=apple&animal=bear
-------------------
with equals
foo=bar&baz=quux&equals=with=extra=equals&grault=garply
{"grault":"garply","equals":"with=extra=equals","baz":"quux","foo":"bar"}
grault=garply&equals=with%3Dextra%3Dequals&baz=quux&foo=bar
-------------------
no value
foo=bar&baz=&qux=quux
{"qux":"quux","baz":"","foo":"bar"}
qux=quux&baz=&foo=bar
-------------------
value omit
foo=bar&baz&qux=quux
{"qux":"quux","foo":"bar"}   <-- it's there, i swear!
qux=quux&baz=&foo=bar        <-- ...see, jQuery found it
-------------------