Gets a query string parameter.

get-query-string-parameter.js

/** Gets a query string parameter.
@returns {String|null} Returns the value of the query string parameter, or null if that parameter is not defined.
*/
function getQueryStringParameter(/** {String} */ key) {
	var keyRe, match, output = null;
	if (document.location.search.length) {
		keyRe = new RegExp(key + "=([^\\&]+)", "i");
		match = document.location.search.match(keyRe);
		if (match) {
			output = match[1];
			console.log(key, output);
		}
	}
	return output;
}