style.js

window.addEventListener("keydown", function(e) {
        const audio = document.querySelector(`audio[data-key="${e.keyCode}"]`);
        const key = document.querySelector(`.key[data-key="${e.keyCode}"]`);

        if (!audio) return;
        audio.currentTime = 0;
        audio.play();
        key.childNodes[1].classList.add('playing');
        setTimeout(function() {
            key.childNodes[1].classList.remove('playing');
        }, 90);
    })
    /*
    let about = document.getElementById('contacts');
    about.addEventListener("click", function(){
        document.getElementById('contact').style.visibility= "visible";
        document.getElementById('btn').style.visibility = "visible";
    })

    document.getElementById('btn').addEventListener("click", function(){
        document.getElementById('contact').style.visibility= "hidden";
        this.style.visibility= "hidden";
    })
    */
var TxtRotate = function(el, toRotate, period) {
    this.toRotate = toRotate;
    this.el = el;
    this.loopNum = 0;
    this.period = parseInt(period, 10) || 2000;
    this.txt = '';
    this.tick();
    this.isDeleting = false;
};

TxtRotate.prototype.tick = function() {
    var i = this.loopNum % this.toRotate.length;
    var fullTxt = this.toRotate[i];

    if (this.isDeleting) {
        this.txt = fullTxt.substring(0, this.txt.length - 1);
    } else {
        this.txt = fullTxt.substring(0, this.txt.length + 1);
    }

    this.el.innerHTML = '<span class="wrap">' + this.txt + '</span>';

    var that = this;
    var delta = 300 - Math.random() * 100;

    if (this.isDeleting) { delta /= 2; }

    if (!this.isDeleting && this.txt === fullTxt) {
        delta = this.period;
        this.isDeleting = true;
    } else if (this.isDeleting && this.txt === '') {
        this.isDeleting = false;
        this.loopNum++;
        delta = 500;
    }

    setTimeout(function() {
        that.tick();
    }, delta);
};

window.onload = function() {
    var elements = document.getElementsByClassName('txt-rotate');
    for (var i = 0; i < elements.length; i++) {
        var toRotate = elements[i].getAttribute('data-rotate');
        var period = elements[i].getAttribute('data-period');
        if (toRotate) {
            new TxtRotate(elements[i], JSON.parse(toRotate), period);
        }
    }
    // INJECT CSS
    var css = document.createElement("style");
    css.type = "text/css";
    css.innerHTML = ".txt-rotate > .wrap { border-right: 0.08em solid #666 }";
    document.body.appendChild(css);
};