Go to next input field at maxLength?

I have a form in Vue that has some combined inputs for styling reasons for a phone number input.

My problem is that the user has to hit tab in order to go to the next input field of the phone number.

Is there a way to check for the max length of the current and input and when that is met go to the next input?

<div class="combined-input combined-input--phone" :class="{'error--input': phoneInvalid('patientInformation')}">
  <div class="open-parenthesis"></div>

  <input type="text" id="phoneArea" maxlength="3" @blur="$v.formData.patientInformation.phone.$touch()" v-model.trim="$v.formData.patientInformation.phone.area.$model">

  <div class="close-parenthesis"></div>

  <input type="text" id="phoneA" maxlength="3" @blur="$v.formData.patientInformation.phone.$touch()" v-model.trim="$v.formData.patientInformation.phone.a.$model">

  <div class="dash"></div>

  <input type="text" id="phoneB" maxlength="4" @blur="$v.formData.patientInformation.phone.$touch()" v-model.trim="$v.formData.patientInformation.phone.b.$model">
</div>

Answer

Pretty sure this is not recommended UX-wise but here is an example on how you can achieve it: https://codesandbox.io/s/move-to-next-input-on-condition-103b5?file=/src/App.vue

The main part of useful code is

focusNextOncePopulated(event, max) {
  if (event.target.value.length === max) {
    const nextElement = this.$refs?.[`input-${Number(event.target.dataset.index) +1}`]
    if (nextElement) nextElement.focus()
  }
},

Explanation: each time you input a char, you check if the length of the field reached the maximum you’ve set on a particular input. If it is and there is a similar input as a sibling, you focus it.
Adding a debounce of a few milliseconds would be nice too, performance-wise.

EDIT: to prevent any issues of trying to find the correct next input in the DOM, we setup some refs on each of the inputs (recommended way in Vue to select some DOM elements). Then, when we have reached the max, we increment our current’s input data-index by one, which enables us to go to the next input.

PS: ?. syntax is optional chaining, it prevents ugly code and allows to avoid an error if there is no next input once max is reached.

PS: Not sure if there is a way to directly get the $refs of an element on it’s @input event but if there is, I didn’t found out how to do it.