index.js

var num = document.querySelectorAll(".drum").length;

for(var i=0; i<num; i++){
    document.querySelectorAll(".drum")[i].addEventListener("click",function(){
    
    var buttonInner = this.innerHTML;
    
    makesound(buttonInner);
    animation(buttonInner);

});
}

document.addEventListener("keydown",function(event){
    
    makesound(event.key);
    animation(event.key);

});

function makesound(key){
    switch (key) {
        case "w":
            var tom1 = new Audio('sounds/tom-1.mp3');
            tom1.play();
            break;
        case "a":
            var tom2 = new Audio('sounds/tom-2.mp3');
            tom2.play();
            break;
        case "s":
            var tom3 = new Audio('sounds/tom-3.mp3');
            tom3.play();
            break;
        case "d":
            var tom4 = new Audio('sounds/tom-4.mp3');
            tom4.play();
            break;
        case "j":
            var snare = new Audio('sounds/snare.mp3');
            snare.play();
            break;
        case "k":
            var crash = new Audio('sounds/crash.mp3');
            crash.play();
            break;
        case "l":
            var kick = new Audio('sounds/kick-bass.mp3');
            kick.play();
            break;                    
        default: console.log(buttonInner);
            break;
    }

}

function animation(currentKey){ 

   var activebutton = document.querySelector("."+currentKey);
   
   activebutton.classList.add("pressed");
   setTimeout(function(){
        activebutton.classList.remove("pressed");
   }, 100);

}