on input change code example

Example 1: dropdown option selection change event in jquery

$("select [name='element_name']").change(function(){
	// condition goes here
});

Example 2: javascript input value change

function updateInput(ish){
    document.getElementById("fieldname").value = ish;
}

Example 3: on change event html not working

onchange is only triggered when the control is blurred. Try onkeypress instead.