Change form values after submit button pressed

Question

[EDIT] After a lot of digging around, I found out that the problem was in how I integrated the CKEditor into my page. The simple and obvious way does work in this case, as laid out in the accepted answer.

Hi,

I need to change the values of a form, after the submit button has been pressed, but before the actual submission has taken place.

I've tried hooking into the "submit" event of the form, and changing the text field values there manually, but it looks like that doesn't actually change the values submitted.

Any ideas?

Solution 1

I'm curious about your statement that the submit handler didn't work for you. It does for me. I've used it for years to fill in hidden fields before sending forms in; should work for other form fields as well.

Example (live copy):

HTML:

<form id='theForm'
    action='http://www.google.com/search'
    method='GET' target='_new'>
      <label>Search for:
        <input type='text' name='q' id='txtSearch'></label>
      <input type='submit' id='btnSearch' value='Search'>

JavaScript:

window.onload = function() {

  document.getElementById('theForm').onsubmit = function() {
    var txt = document.getElementById('txtSearch');
    txt.value = "updated " + txt.value;
  };
};​

Tested and working on IE6 and IE7 on Windows, and Chrome, Firefox, and Opera on Linux.

---

Update: Based on your comment below, you're using jQuery. Works fine using jQuery for everything as well:

$('#theForm').submit(function() {
  var txt = $('#txtSearch');
  txt.val("updated " + txt.val());
});

Live example Tested and working on the same set of browsers. This version uses a more open search rather than an id, and also still works.

Solution 2

You need to prevent the default submit action and then resubmit the form yourself manually:

$('form').submit(function(e) {
    e.preventDefault();

    // do your processing

    this.submit(); // call the submit function on the element rather than 
                   // the jQuery selection to avoid an infinite loop
});

Comments

[T.J. Crowder]

@David: The submit function on form elements doesn't trigger the submit handler. (Note it's this.submit(); not $(this).submit();').

[Sikshya Maharjan]

@T.J., yeah, it might be simple, but I wouldn't have thought of doing it that way; so it's still worth the +1 for teaching me something I didn't know =)

[T.J. Crowder]

"You need to prevent the default submit action and then resubmit the form yourself manually" I don't think you do. I think the OP is mistaken about the submit handler. I've used it for years to fill in hidden fields before sending forms in.

[Editorman]

I'm not sure why it doesn't work for me. Likely I'm just doing something wrong. But using lonesomeday's method makes the same code I had before work, so thanks!

[Editorman]

OK I checked again, with your code it works. The difference - I was using jQuery to get and set the text box (i.e., $('.txtSearch').val(newval)). Changing it to this solved it: $(".txtSearch")[0].value = newval. Any idea what the difference is?

[Editorman]

OK forget my previous message - T.J. Crowder is right, it's possible to do this without resubmitting the form. Also, this solution caused me problems (something to do with an invalid token in the cookies - I have no idea what exactly caused it.)

[T.J. Crowder]

@Editorman: Nope, it should come down to the same thing. I translated my example to use jQuery for everything and it still works, see above.

[Editorman]

OK, see the update in the question. The problem was, half the time I tested with the CKEditor, and half the time without (obviously without realizing it!), which meant that your methods, my methods, everyone's methods worked, but only half the time! Thanks for the help in any case..

[Matt Wonlaw]

One issue you'll have: if the user presses back they will see the altered value in the form instead of the value they entered. You can get around this by doing this in the onSubmit event: onsubmit = function() { var oldText = elem.value; elem.value = "updated" + elem.value; setTimeout(function() { elem.value = oldText; }, 0); }