Dynamic mask for CPF, CNPJ and CEI fields

Question

Hello, I looked for this doubt in the questions, but I could not find it. Well, I would like to make a field to have the masks of CPF and CNPJ and CEI. depending on the number of characters typed. Here it doesn’t work totally well, because with several tests I did here, this my code didn’t work that I need. I don’t know if I should just change, or if I need to make another.

The format of the ERC is: 00.000.00000/00

I tried this code, but without any success:

$(".cpf_cnpj_cei").mask("000.000.000-00", {
  onKeyPress: function(cpfcnpj, e, field, options) {
    const masks = ["000.000.000-00", "00.000.00000/00", "00.000.000/0000-00"];
    let mask = null;
    if (cpfcnpj.length < 14) {
      mask = masks[0];
    } else if (cpfcnpj.length > 14 && cpfcnpj.length < 18) {
      mask = masks[1];
    } else if (cpfcnpj.length > 18) {
      mask = masks[2];
    }
    $(".cpf_cnpj_cei").mask(mask, options);
  }
});

<input class="cpf_cnpj_cei" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.0/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery.mask/1.14.15/jquery.mask.min.js"></script>

REFERENCES
Mask for CPF and CNPJ in the same field. Mask for CPF and CNPJ in the same field
CIS generator: https://theonegenerator.com/pt/geradores/documentos/gerador-de-cei
jQuery Mask Plugin A plugin to make masks on form Fields. https://igorescobar.github.io/jQuery-Mask-Plugin/

Answer 1

Mask limits the number of characters, as you start with a Cpf mask "000.000.000-00" the input will never have more than 14 characters. Put the masks with an extra zero, so that the user can continue typing.

And in this case specifically and modify/simplify the logics to be "less or equal" and the latter to a Else, now as soon as the 16th character is typed it already shows the CNPJ mask

$(".cpf_cnpj_cei").mask("000.000.000-00", {
  onKeyPress: function(cpfcnpj, e, field, options) {
    const masks = ["000.000.000-000", "00.000.00000/000", "00.000.000/0000-00"];
    let mask = null;
    if (cpfcnpj.length <= 14) {
      mask = masks[0];
    } else if (cpfcnpj.length <= 15) {
      mask = masks[1];
    } else {
      mask = masks[2];
    }
    $(".cpf_cnpj_cei").mask(mask, options);
  }
});

<input class="cpf_cnpj_cei" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.0/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery.mask/1.14.15/jquery.mask.min.js"></script>