onchange="myFunction(document.getElementById("myId"))"

onchange="myFunction(document.getElementById("myId"))"

onchange="myFunction(document.getElementById('myId'))"

onchange="myFunction(document.getElementById('myId'))";

onchange="myFunction()"

function myFunction(){
    var target_id = document.getElementById("myId").value;
    ....
}

onchange="myFunction(this.id)"

onchange=myFun(this.value) or onchange="myFun(this.value)"