Javascript Input Text Masking without Plugin

Question

I want to mask the text in an input box without changing the actual value. I can not use any plugins.

I am currently doing this - but as you can see the issue is tha

Answer 1

or also

with

function handleMask(event, mask) {
    with (event) {
        stopPropagation()
        preventDefault()
        if (!charCode) return
        var c = String.fromCharCode(charCode)
        if (c.match(/\D/)) return
        with (target) {
            var val = value.substring(0, selectionStart) + c + value.substr(selectionEnd)
            var pos = selectionStart + 1
        }
    }
    var nan = count(val, /\D/, pos) // nan va calcolato prima di eliminare i separatori
    val = val.replace(/\D/g,'')

    var mask = mask.match(/^(\D*)(.+9)(\D*)$/)
    if (!mask) return // meglio exception?
    if (val.length > count(mask[2], /9/)) return

    for (var txt='', im=0, iv=0; im