JavaScript - auf jQuery warten und ggf. nachladen

// Wegner's jQuery Script => Check, load and execute
function waitOnjQuery(index = 0) {
    if (checkjQueryReady()) {
        MainScript();
    } else {
        if (index <= 1) {
            insertjQuery();
        }
        setTimeout(function () {
            waitOnjQuery(++index);
        }, 200);
    }
}
function checkjQueryReady() {
    if (typeof jQuery == 'function') {
        return true;
    }
    return false;
}
function insertjQuery(version = "1.7.1") {
    var jQueryScript = document.createElement("script");
    jQueryScript.src = "https://ajax.googleapis.com/ajax/libs/jquery/" + version + "/jquery.min.js";
    document.getElementsByTagName("head")[0].appendChild(jQueryScript);
}
function MainScript() {
    // Paste your code here
}
waitOnjQuery();