[html] How do you overcome the HTML form nesting limitation?

I know that XHTML doesn't support nested form tags and I have already read other answers here on Stack Overflow regarding this subject, but I still haven't figured out an elegant solution to the problem.

Some say you don't need it and that they can't think of a scenario were this would be needed. Well, personally I can't think of a scenario that I haven't needed it.

Let's see a very simple example:

You are making a blog app and you have a form with some fields for creating a new post and a toolbar with "actions" like "Save", "Delete", "Cancel".

<form
 action="/post/dispatch/too_bad_the_action_url_is_in_the_form_tag_even_though_conceptually_every_submit_button_inside_it_may_need_to_post_to_a_diffent_distinct_url"
method="post">

    <input type="text" name="foo" /> <!-- several of those here -->
    <div id="toolbar">
        <input type="submit" name="save" value="Save" />
        <input type="submit" name="delete" value="Delete" />
        <a href="/home/index">Cancel</a>
    </div>
</form>

Our objective is to write the form in a way that doesn't require JavaScript, just plain old HTML form and submit buttons.

Since the action URL is defined in the Form tag and not in each individual submit button, our only option is to post to a generic URL and then start "if...then...else" to determine the name of the button that was submitted. Not very elegant, but our only choice, since we don't want to rely on JavaScript.

The only problem is that pressing "Delete", will submit ALL the form fields on the server even though the only thing needed for this action is a Hidden input with the post-id. Not very big deal in this small example, but I have forms with hundreds (so to speak) of fields and tabs in my LOB applications that (because of requirements) have to submit everything in one-go and in any case this seems very inefficient and a waste. If form nesting was supported, I would at least be able to wrap the "Delete" submit button inside it's own form with only the post-id field.

You may say "Just implement the "Delete" as a link instead of submit". This would be wrong in so many levels, but most importantly because Side-effect actions like "Delete" here, should never be a GET request.

So my question (particularly to those that say they haven't needed form nesting) is What do YOU do? Is there any elegant solution that I'm missing or the bottom line is really "Either require JavaScript or submit everything"?

HTML5 has an idea of "form owner" - the "form" attribute for input elements. It allows to emulate nested forms and will solve the issue.

Use an iframe for the nested form. If they need to share fields, then... it's not really nested.

In response to a question posted by Yar in a comment to his own answer, I present some JavaScript which will resize an iframe. For the case of a form button, it is safe to assume the iframe will be on the same domain. This is the code I use. You will have to alter the maths/constants for your own site:

function resizeIFrame(frame)
{
    try {
        innerDoc = ('contentDocument' in frame) ? frame.contentDocument : frame.contentWindow.document;
        if('style' in frame) {
            frame.style.width = Math.min(755, Math.ceil(innerDoc.body.scrollWidth)) + 'px';
            frame.style.height = Math.ceil(innerDoc.body.scrollHeight) + 'px';
        } else {
            frame.width = Math.ceil(innerDoc.body.scrollWidth);
            frame.height = Math.ceil(innerDoc.body.scrollHeight);
        }
    } catch(err) {
        window.status = err.message;
    }
}

Then call it like this:

<iframe ... frameborder="0" onload="if(window.parent && window.parent.resizeIFrame){window.parent.resizeIFrame(this);}"></iframe>

I went around the issue by including a checkbox depending on what form the person wanted to do. Then used 1 button to submit the whole form.

If you really don't want to use multiple forms (as Jason sugests), then use buttons and onclick handlers.

<form id='form' name='form' action='path/to/add/edit/blog' method='post'>
    <textarea name='message' id='message'>Blog message here</textarea>
    <input type='submit' id='save' value='Save'>
</form>
<button id='delete'>Delete</button>
<button id='cancel'>Cancel</button>

And then in javascript (I use jQuery here for easyness) (even though it is pretty overkill for adding some onclick handlers)

$('#delete').click( function() {
   document.location = 'path/to/delete/post/id'; 
});
$('#cancel').click( function() {
   document.location = '/home/index';
});

Also I know, this will make half the page not work without javascript.

I just came up with a nice way of doing it with jquery.

<form name="mainform">    
    <div id="placeholder">
    <div>
</form>

<form id="nested_form" style="position:absolute">
</form>

<script>
   $(document).ready(function(){
      pos = $('#placeholder').position();
      $('#nested_form')
         .css('left', pos.left.toFixed(0)+'px')
         .css('top', pos.top.toFixed(0)+'px');
   });
</script>

can you have the forms side by side on the page, but not nested. then use CSS to make all the buttons line up pretty?

<form method="post" action="delete_processing_page">
   <input type="hidden" name="id" value="foo" />
   <input type="submit" value="delete" class="css_makes_me_pretty" />
</form>

<form method="post" action="add_edit_processing_page">
   <input type="text" name="foo1"  />
   <input type="text" name="foo2"  />
   <input type="text" name="foo3"  />
   ...
   <input type="submit" value="post/edit" class="css_makes_me_pretty" />
</form>

Alternatively you could assign the form actiob on the fly...might not be the best solution, but sure does relieve the server-side logic...

<form name="frm" method="post">  
    <input type="submit" value="One" onclick="javascript:this.form.action='1.htm'" />  
    <input type="submit" value="Two" onclick="javascript:this.form.action='2.htm'" />  
</form>

This discussion is still of interest to me. Behind the original post are "requirements" which the OP seems to share - i.e. a form with backward compatibility. As someone whose work at the time of writing must sometimes support back to IE6 (and for years to come), I dig that.

Without pushing the framework (all organizations are going to want to reassure themselves on compatibility/robustness, and I'm not using this discussion as justification for the framework), the Drupal solutions to this issue are interesting. Drupal is also directly relevant because the framework has had a long time policy of "it should work without Javascript (only if you want)" i.e. the OP's issue.

Drupal uses it's rather extensive form.inc functions to find the triggering_element (yes, that's the name in code). See the bottom of the code listed on the API page for form_builder (if you'd like to dig into details, the source is recommended - drupal-x.xx/includes/form.inc). The builder uses automatic HTML attribute generation and, via that, can on return detect which button was pressed, and act accordingly (these can be set up to run separate processes too).

Beyond the form builder, Drupal splits data 'delete' actions into separate URLs/forms, likely for the reasons mentioned in the original post. This needs some sort of search/listing step (groan another form! but is user-friendly) as a preliminary. But this has the advantage of eliminating the "submit everything" issue. The big form with the data is used for it's intended purpose, data creation/updating (or even a 'merge' action).

In other words, one way of working around the problem is to devolve the form into two, then the problem vanishes (and the HTML methods can be corrected through a POST too).

Kind of an old topic, but this one might be useful for someone:

As someone mentioned above - you can use a dummy form. I had to overcome this issue some time ago. At first, I totally forgot about this HTML restriction and just added the nested forms. The result was interesting - I lost my first form from the nested. Then it turned out to be some kind of a "trick" to simply add a dummy form (that will be removed from the browser) before the actual nested forms.

In my case it looks like this:

<form id="Main">
  <form></form> <!--this is the dummy one-->
  <input...><form id="Nested 1> ... </form>
  <input...><form id="Nested 1> ... </form>
  <input...><form id="Nested 1> ... </form>
  <input...><form id="Nested 1> ... </form>
  ......
</form>

Works fine with Chrome, Firefox, and Safari. IE up to 9 (not sure about 10) and Opera does not detect parameters in the main form. The $_REQUEST global is empty, regardless of the inputs. Inner forms seem to work fine everywhere.

Haven't tested another suggestion described here - fieldset around nested forms.

EDIT: Frameset didn't work! I simply added the Main form after the others (no more nested forms) and used jQuery's "clone" to duplicate inputs in the form on button click. Added .hide() to each of the cloned inputs to keep layout unchanged and now it works like a charm.

I think Jason's right. If your "Delete" action is a minimal one, make that be in a form by itself, and line it up with the other buttons so as to make the interface look like one unified form, even if it's not.

Or, of course, redesign your interface, and let people delete somewhere else entirely which doesn't require them to see the enormo-form at all.

My solution is to have the buttons call JS functions which write and then submit forms outwith the main form

<head>
<script>
function removeMe(A, B){
        document.write('<form name="removeForm" method="POST" action="Delete.php">');
        document.write('<input type="hidden" name="customerID" value="' + A + '">');
        document.write('<input type="hidden" name="productID" value="' + B + '">');
        document.write('</form>');
        document.removeForm.submit();
}
function insertMe(A, B){
        document.write('<form name="insertForm" method="POST" action="Insert.php">');
        document.write('<input type="hidden" name="customerID" value="' + A + '">');
        document.write('<input type="hidden" name="productID" value="' + B + '">');
        document.write('</form>');
        document.insertForm.submit();
}
</script>
</head>

<body>
<form method="POST" action="main_form_purpose_page.php">

<input type="button" name="remove" Value="Remove" onclick="removeMe('$customerID','$productID')">
<input type="button" name="insert" Value="Insert" onclick="insertMe('$customerID','$productID')">

<input type="submit" name="submit" value="Submit">
</form>
</body>

I know this is an old question, but HTML5 offers a couple new options.

The first is to separate the form from the toolbar in the markup, add another form for the delete action, and associate the buttons in the toolbar with their respective forms using the form attribute.

<form id="saveForm" action="/post/dispatch/save" method="post">
    <input type="text" name="foo" /> <!-- several of those here -->  
</form>
<form id="deleteForm" action="/post/dispatch/delete" method="post">
    <input type="hidden" value="some_id" />
</form>
<div id="toolbar">
    <input type="submit" name="save" value="Save" form="saveForm" />
    <input type="submit" name="delete" value="Delete" form="deleteForm" />
    <a href="/home/index">Cancel</a>
</div>

This option is quite flexible, but the original post also mentioned that it may be necessary to perform different actions with a single form. HTML5 comes to the rescue, again. You can use the formaction attribute on submit buttons, so different buttons in the same form can submit to different URLs. This example just adds a clone method to the toolbar outside the form, but it would work the same nested in the form.

<div id="toolbar">
    <input type="submit" name="clone" value="Clone" form="saveForm"
           formaction="/post/dispatch/clone" />
</div>

http://www.whatwg.org/specs/web-apps/current-work/#attributes-for-form-submission

The advantage of these new features is that they do all this declaratively without JavaScript. The disadvantage is that they are not supported on older browsers, so you'd have to do some polyfilling for older browsers.

Well, if you submit a form, browser also sends a input submit name and value. So what yo can do is

<form   
 action="/post/dispatch/too_bad_the_action_url_is_in_the_form_tag_even_though_conceptually_every_submit_button_inside_it_may_need_to_post_to_a_diffent_distinct_url"  
method="post">  

    <input type="text" name="foo" /> <!-- several of those here -->  
    <div id="toolbar">
        <input type="submit" name="action:save" value="Save" />
        <input type="submit" name="action:delete" value="Delete" />
        <input type="submit" name="action:cancel" value="Cancel" />
    </div>
</form>

so on server side you just look for parameter that starts width string "action:" and the rest part tells you what action to take

so when you click on button Save browser sends you something like foo=asd&action:save=Save

One way I would do this without javascript would be to add a set of radio buttons that define the action to be taken:

• Update
• Delete
• Whatever

Then the action script would take different actions depending on the value of the radio button set.

Another way would be to put two forms on the page as you suggested, just not nested. The layout may be difficult to control though:

<form name="editform" action="the_action_url"  method="post">
   <input type="hidden" name="task" value="update" />
   <input type="text" name="foo" />
   <input type="submit" name="save" value="Save" />
</form>

<form name="delform" action="the_action_url"  method="post">
   <input type="hidden" name="task" value="delete" />
   <input type="hidden" name="post_id" value="5" />
   <input type="submit" name="delete" value="Delete" />
</form>

Using the hidden "task" field in the handling script to branch appropriately.