A simple function to return a hash with parameters, parsed from a query string.

get_query_params.js

// Returns a hash with the query parameters, parsed from the query string given
// (or the current location's query string, if no arguments given)
// Based on code found here:
// http://stackoverflow.com/questions/901115/get-querystring-values-in-javascript/2880929#2880929
function getQueryParams(queryString) {
	var queryParams = {},
		e,
		r = /([^&=]+)=?([^&]*)/g,
		d = function (s) { return decodeURIComponent(s.replace(/\+/g, ' ')); },
		q = queryString || window.location.search.substring(1);

	while (e = r.exec(q)) {
	   queryParams[d(e[1])] = d(e[2]);
	}

	return queryParams;
}

Using regex for this is just wrong and will fail in some scenarios.

You'd better off using a tiny reusable module like:
https://github.com/sindresorhus/query-string