Optimize setting parameters from query string
You are correct that it would be much faster to parse all the parameters once into an object and then just access them from there rather than refind every single parameter from scratch each time:

function getParameters(sourceURL) {
    var pairs, parts, i, output = {};
    sourceURL = sourceURL || window.location.search;
    // strip off leading ?
    if (sourceURL.charAt(0) === "?") {
        sourceURL = sourceURL.slice(1);
    }
    // split into individual pairs
    pairs = sourceURL.split("&amp;");
    for (i = 0; i &lt; pairs.length; i++) {
        // split each pair
        parts = pairs[i].split("=");
        if (parts.length &lt; 2) {
            parts.push("");
        }
        // make key always be lowercase and store key/value pair
        output[decodeURIComponent(parts[0]).toLowerCase()] = decodeURIComponent(parts[1]);
    }
    return output;
}

var params = getParameters();


Then, you can fetch an individual parameter anytime from the params object.  In fact, you won't even need to store them all in globals since there already stored in this one variable.

var Query_MenuTiles = params["menutiles"];


Working demo: http://jsfiddle.net/jfriend00/pj5ocazd/