requestSubmit offers a way to validate a form before submit

HTML form elements are the foundation for the interactions in web pages. And they improved quite a little bit over the last years. Today, developers can use different types (number, tel, color, ...) and set different input modes (text, decimal, email, ...) to name two examples.

What remained tricky was to submit forms from within the scope of JavaScript. The HTMLFormElement defines a submit method, but it does not quite behave as one would expect.

Let's assume we have the following HTML form:

<form action="">
  <label>
    Your name
    <input type="text" required>
  </label>
  <button>Submit</button>
</form>

And some JavaScript:

document.querySelector('form')
  .addEventListener('submit', (event) => {
    // don't submit the form and
    // only log to the console
    event.preventDefault();
    console.log('submitted form');
  });

When one clicks the submit button the following happens:

1. the form is validated and possible errors are shown
2. if the form validation passes and the form is valid, it fires a submit event
3. the submit handler is called and it prevents the form submission due to event.preventDefault()

This triggered submit event gives developers a way to react to form submissions in JavaScript. And it's used a lot! Common scenarios in modern applications are to call preventDefault, make AJAX requests using JavaScript and replace the page contents dynamically.

But what happens when you access the form from the DOM and submit it in JavaScript via submit?

document.querySelector('form').submit();

The answer is – the form is submitted! (🤦‍♂️ duh!) What's surprising is that there won't be input and form validation, and there won't be a submit event. All the values are submitted no matter if the inputs are valid or not. This is unexpected behavior and it should behave like pressing the submit button. There are surely reason for skipping the validation, but I'd expect that submit also validates the form and only proceeds if everything is valid.

You can work around this problem by triggering the click on the submit button. The click then triggers the standard behavior that users see when they interact with a form, including validations and a fired submit event.

Mimicking user behavior works fine and that's great – case closed! But I never thought of this solution as elegant or pretty. It turns out there's a better way.

People started to work on a solution to this behavior in June 2019 (the proposal is an interesting read). The HTMLFormElement now includes a new method called requestSubmit. And this method does the same as clicking a submit button. 🎉

There is no magic to it – the JavaScript method does what you expect and offers the great goodies HTML forms ship by default (including the form validation). I have to say – I'm excited about it!

The method's browser support as of March 2021 is as follows:

• ✅ Chromium browsers (the new Microsoft Edge, Chrome, Opera, ...)
• ✅ Firefox
• ❌ Safari

Unfortunately, requestSubmit is not cross browser supported yet. Luckily, a quick Google search brought up a requestSubmit polyfill (I didn't test it, but the code looks fine).

You can read more about the requestSubmit method on MDN, dive into its specification or see it in action on CodePen.

You can see a #devsheet visualizing the difference in the video below.

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