requestSubmit offers a way to validate a form before submit
- Published at
- Updated at
- Reading time
- 3min
This post is part of my Today I learned series in which I share all my learnings regarding web development.
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:
- the form is validated and possible errors are shown
- if the form validation passes and the form is valid, it fires a
submit
event - the
submit
handler is called and it prevents the form submission due toevent.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!
submit | requestSubmit |
---|---|
doesn't trigger submit event | triggers submit event |
doesn't trigger form validation | triggers form validation |
can't be canceled | can be canceled via event.preventDefault in a submit event handler |
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.
If you're interested in reading more quick TIL ("today i learned") posts, subscribe to my weekly newsletter. 👋