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Differences between requestSubmit() and submit() in HTML forms

The most used way to programmatically submit an HTML form with Javascript is the submit method:

<form>   
  <input required name="email" id="email" type="email" placeholder="Email here ...">
  <input type="submit" class="submit-btn" value="Use submit()" />
</form>
const form = document.forms[0]
document.querySelector('.submit-btn')
  .addEventListener('click', () => form.submit()
    form.submit())

However, it has (at least) 2 unexpected behaviors:

  1. submit will bypass the validation of the form. This means that the above form will be subbitment even if we have the required attribute set on the email input and that input is empty.
    // submit() will not take into account the required attr
    <input required name="email" id="email" type="email" >
  2. if we a add addEventListener('submit') to the form submit will also bypass it. For example:
    form.addEventListener('submit', e => {
    // this code will not be called when using submit()
    e.preventDefault()
    alert('Code after preventDefault called')
    })

Now with a full browser support, requestSubmit method aims to provide an more predictable behaivour to our form submisons. The requestSubmit() will take into account both the native form validation and it alows interceptions with addEventListener('submit').

form.addEventListener('submit', e => {
  // this will be called only 
  // when using requestSubmit()
  e.preventDefault()
  alert('Code after preventDefault called')
})

document.querySelector('.submit-btn')
  .addEventListener('click', () => form.submit()
    form.submit())

// requestSubmit() will first check for form validation
document.querySelector('.requestSubmit-btn')
  .addEventListener('click', () => form.requestSubmit())

Checkout a working codepen here.

And speaking of submitting forms I've also made this example of how to use the FormData Api and append extra data to it and what errors you can get.

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