How do I stop a remote form from submitting?

问题

I have a form that can be used both remotely and normally.

= form_for @comment, html: { class: 'comment-form' }, remote: request.xhr? do |f|
  = f.text_area :body
  = f.submit

I want the form to submit only if the body textarea has content:

  $(document).on 'submit', '.comment-form', (e) ->
    text = $(this).find('#comment_body').val()
    false if text.length < 1

That code works when the form is not Ajax. But when it's remote, it fails and the form still submits. Why? I also tried:

if text.length < 1
  e.preventDefault()
  false

I'm using Rails 4 with Turbolinks.

Update: I tried binding the ajax:beforeSend event, it still submits:

  $(document).on 'page:load', '.comment-form', ->
    $(this).bind 'ajax:beforeSend', ->
      alert "hi"

I see no alert...

回答1:

You could potentially implement a handler for the ajax:beforeSend event to prevent your form from being submitted. It looks like the submit stops if your event handler returns false.

Wiki: https://github.com/rails/jquery-ujs/wiki/ajax

Example implementation: Stop $.ajax on beforeSend

回答2:

I'm using Rails 5.0.0.1 and as described at jquery-ujs documentation in Stoppable events section you only need to return a false value in the ajax:beforeSend event to stop the request and prevent the form from being send.

So this works perfectly for me:

$(document).on("ajax:beforeSend", "form#messages_form", function (e, data, status, xhr) {
    var len = $.trim($('#message_body').val()).length;

    if (len > 3) {
        console.log("Send form!");
        return true;
    } else {
        console.log("Stopping request...");
        return false;
    }
});

I hope it could be useful for somebody else.