Disabling things and re enabling them

[cpd]

I want to disable a submit button until an input box is typed in.

 

How do i do this?

[rhodesa]

<form>
  <input type="text" name="foobar" onkeyup="this.form['my_submit'].disabled = !this.value.length;" />
  <input type="submit" name="my_submit" disabled=true />
</form>

[cpd]

Aww thats awesome dude cheers, ive just gotta make another thing in PHP that tests something else because its baisically for a shoutbox but i dont want them to submit the value thats already in the box and whats above works fine however.

 

if you hit f5 to refresh the page it enters the comment you last entered which is annoying. So i need to test if its the same as the last comment which wont work

[rhodesa]

right, so you can just do:

<form>
  <input type="text" id="foobar" name="foobar" onkeyup="checkInput(this);" />
  <input type="submit" name="my_submit" />
</form>
<script type="text/javascript">
function checkInput(ele){
  ele.form['my_submit'].disabled = !ele.value.length;
}
checkInput(document.getElementById('foobar'));
</script>