Problem

A javascript should read the browsers address bar to get GET Üarameters that have been appended to the adress bar.

Approach – Ansatz

Usage of decodeURIComponent

Solution

var getUrlParameter = function getUrlParameter(sParam) {
	var sPageURL = decodeURIComponent(window.location.search.substring(1)),
		sURLVariables = sPageURL.split('&'),
		sParameterName,
		i;

	for (i = 0; i < sURLVariables.length; i++) {
		sParameterName = sURLVariables[i].split('=');

		if (sParameterName[0] === sParam) {
			return sParameterName[1] === undefined ? true : sParameterName[1];
		}
	}
};

var myMap = getUrlParameter("map");
if (myMap) {
	diagramType = myMap;
}

You can call now the script like this:
http://webseite.html?map=Test