Change value of input onchange?

Question

I am trying to create a simple JavaScript function. When someone inserts a number in an input field, the value of another field should change to that value. Here is what I have at the moment:

function updateInput(ish) {       fieldname.value = ish;   }   <input type="text" name="fieldname" id="fieldname" />   <input type="text" name="thingy" onchange="updateInput(value)" />  

Somehow this does not work, can someone help me out?

Answer 1

You can't access your fieldname as a global variable. Use document.getElementById:

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

and

onchange="updateInput(this.value)" 

Answer 2

for jQuery we can use below:

by input name:

$('input[name="textboxname"]').val('some value'); 

by input class:

$('input[type=text].textboxclass').val('some value'); 

by input id:

$('#textboxid').val('some value');