index.js

var allDrums = document.querySelectorAll(".drum");
for(var index = 0; index < allDrums.length; index++){
    allDrums[index].addEventListener("click", 
        function(event){
            playSound(event.target.textContent);
            playAnimation(event.target.textContent);
        });
}
document.addEventListener("keydown", 
    function(event){
        playSound(event.key);
        playAnimation(event.key);
    });

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

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

// var audio = new Audio("sounds/tom-1.mp3");
// audio.play();