Mask to complete input

Let's suppose I have the following constants declared:

const begin = '1234';
const end = '789';

and I have one html input with preset value='1234-56??-????-0987'

How can I setup a mask (using jQuery-Mask plugin, or not) to:

• When the user inserts any number (for example 7) on the input, the value becomes: 1234-567?-????-0987
• If, after this user inserts '8', it becomes: 1234-5678-????-0987
• When the user replaces all '?', then stop accepting inputs.
• If the user backspaces/erases any digit, the corresponding ? appears again.

Currently I have this code:

const start = '123456';
const end = '0987';
const input = document.getElementById('entry-number');
input.addEventListener('input', () => 
{
    const mask = "******";
    const userInput = input.value.replace(/\D/g, "").replace(start, "").replace(end, "");
    const newNumber = start + userInput + mask.slice(userInput.length) + end;
    input.value = newNumber;
});

But

1. It doesn't respect the mask with hyphens.
2. If I hit backspace, it completely bugs the input value.

The jQuery inputmask plugin could be used to achieve this.

We would use the mask 1234-5699-9999-0\\987. The 99-9999 pattern in (approximately) the middle indicates where arbitrary digits may be entered. The \\9 indicates that this position will have a literal "9" and not an arbitrary digit. We can specify ? as the placeholder value which will be used in the absence of any of the arbitrary digits that can be entered.

$('#entry-number').inputmask({
  mask: '1234-5699-9999-0\\987',
  placeholder: '?'
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/inputmask@5.0.8/dist/jquery.inputmask.min.js"></script>
<input id="entry-number">