Dynamically (Programmatically) JS/CSS file load with callback function

dynamicload.js

// Dynamically (Programmatically) JS/CSS file load with callback function
// Go Namhyeon <[email protected]>

function loadJS(url, callback) {
    var el = document.createElement("script");
    el.src = url;
    el.type = "text/javascript";
    document.head.appendChild(el);
    if(typeof(callback) == "function") {
        el.onload = callback(el);
    }
    return el;
}

function loadCSS(url, callback) {
    var el = document.createElement("link");
    el.href = url;
    el.rel = "stylesheet";
    el.type = "text/css";
    document.head.appendChild(el);
    if(typeof(callback) == "function") {
        el.onload = callback(el);
    }
    return el;
}

// load jQuery and jQuery UI (JS)
loadJS("https://code.jquery.com/jquery-3.4.1.min.js", function(el) {
    alert("JS loaded: " + el.src);
    alert(typeof($));
    loadJS("https://cdnjs.cloudflare.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js", function(el) {
        alert("JS loaded: " + el.src);
    });
});

// load jQuery UI (CSS)
loadCSS("https://cdnjs.cloudflare.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.css", function(el) {
    alert("CSS loaded: " + el.href);
});