How can I change a form's input value with javascript

How can I change a form's input value with javascript depending on witch combobox item is selected. I have a form with some imported values, and there is a field of witch imported value can be changed via a combobox. In my case:

print("<input type='hidden' name='issue_array[{$issue["nr"]}][\"supplier\"]' value='{$issue["supplier"]}' />");

I have a combobox, that if I change it's value, should change the value of the input above.

This is what I tried:

print("<select name开发者_JS百科='supplier_combo' onchange='setSupplierInputValue(this.value, ${issue['nr']})'>");

and the script:

  echo "\r\n" . '<SCRIPT TYPE="text/javascript">' . "\r\n";
  echo 'function setSupplierInputValue(value, issue_nr)' . "\r\n";
  echo '{' . "\r\n";     
  echo '      issue_array[issue_nr]["supplier"] = value;';         
  echo '}' . "\r\n";     
  echo '</SCRIPT>'. "\r\n"; 

But it doesn't work, please help.

change your line

issue_array[issue_nr]["supplier"] = value;

to look like this (you have to select the hidden field by using getElementsByName - or set an id for the hidden field and use getElementById):

document.getElementsByName('issue_array['+issue_nr+']["supplier"]')[0].value = value;

give the combobox an id for example selection and id for the input say inputExample, so using jquery you can

   $('#selection').change(function(){
         //you get the value using $('#selection option:selected').text()
         $('#inputExample').val('somevalue you determined');
    })

I hope it helps. You can also see the reference on jquery site : http://api.jquery.com/change/