index.js

var btn = document.getElementsByClassName("drum");
for (i = 0; i < btn.length; i++) {
    btn[i].addEventListener("click", function (event) {
        makeSound(event.key);
        buttonAnimation(event);
    });
}
// function handleClick(e) {
//     var html = this.innerHTML;
//     makeSound(html);
//     buttonAnimation(e);

// }
document.addEventListener("keypress", function (event) {
    makeSound(event.key);
    buttonAnimation(event);
});
function makeSound(key) {
    switch (key) {
        case 'w':
            var audio = new Audio("sounds/crash.mp3");
            audio.play();
            break;
        case 'a':
            var audio = new Audio("sounds/kick-bass.mp3");
            audio.play();
            break;
        case 's':
            var audio = new Audio("sounds/snare.mp3");
            audio.play();
            break;
        case 'd':
            var audio = new Audio("sounds/tom-1.mp3");
            audio.play();
            break;
        case 'j':
            var audio = new Audio("sounds/tom-2.mp3");
            audio.play();
            break;
        case 'k':
            var audio = new Audio("sounds/tom-3.mp3");
            audio.play();
            break;
        case 'l':
            var audio = new Audio("sounds/tom-4.mp3");
            audio.play();
            break;
        default:
            console.log("click right key");
            break;
    }
}
function buttonAnimation(event){
    var activeButton=document.querySelector("."+event.key);
    activeButton.classList.add("pressed");
    setTimeout(function (){
        activeButton.classList.remove("pressed");
    },100);
}