index.js

for(var i = 0;i<document.querySelectorAll(".drum").length;i++){
    document.querySelectorAll(".drum")[i].addEventListener("click",head);
}
function head(){
    var item = this.innerHTML;
    makesound(item)   
}
document.addEventListener("keypress",function(event){makesound(event.key)});
function makesound(item){
    switch (item){
        case 'a':
            var audio = new Audio("sounds/tom-1.mp3");
            audio.play();
            break;
        case 's':
            var audio = new Audio("sounds/tom-2.mp3");
            audio.play();
            break;
        case 'd':
            var audio = new Audio("sounds/tom-3.mp3");
            audio.play();
            break;
        case 'f':
            var audio = new Audio("sounds/tom-4.mp3");
            audio.play();
            break;
        case 'j':
            var audio = new Audio("sounds/kick-bass.mp3");
            audio.play();
            break;
        case 'k':
            var audio = new Audio("sounds/snare.mp3");
            audio.play();
            break;
        case 'l':
            var audio = new Audio("sounds/crash.mp3");
            audio.play();
            break;
    }
}