for in e for of

<!DOCTYPE html>
<html>
<head>
    <title></title>
</head>
<body>
<script>
    var myArray=[5,10,15,20];

    for(var a in myArray){
        document.write(myArray[a])+"<br>";
    }
    var myObj={
        d:10,
        e:20,
        f:30
    }

    for(var a in myObj){
        document.write(myObj[a]);
    }

    for(var a of myArray){
        document.write(a);
    }
</script>
</body>
</html>