jquery – Cant access then function after getJSON in Javascript

can someone tell why js is not going into the .then( functions?
I need funcParam getting setted after JSon stuff is ready, because otherwise, funcParam will receive values from previouse coderuns.

if (type == "config") {
        getParamsByConfig().then(function(config){
            markerNameByConfig = config[0].name;
            markerCommentByConfig = config[0].description;
            markerDurationByConfig = config[0].duration;
            markerColorByConfig = config[0].color;
            alert(funcParam);
            funcParam = "'"+markerNameByConfig+"', '"+markerCommentByConfig+"', '"+markerDurationByConfig+"', '"+markerColorByConfig+"'";
        });
    }

function getParamsByConfig() {
    //get all Configvalues
    configurationName = document.getElementById('config').value.toString();
    return $.getJSON("../savedConfigs/"+configurationName+".json").then(function(config) {
        alert(config.toString());
        return config;
    });
}