Gets a unique URL to avoid browser cache

cache_buster.js

function cache_buster(url) {
    cache_buster.nonce = cache_buster.nonce || 1;
    var sep = "?";
    var qpos = url.indexOf("?");
    if (url.length === 0 || qpos === url.length-1) {
      sep = "";
    } else if (qpos >= 0) {
        sep = "&";
    }
    return url + sep + "nocache=" + (new Date()).getTime() + "-" + cache_buster.nonce++;
}