Regex phone masking

Question

I'm trying to write phone input masking function. Here it is:

let input = document.querySelector('input');

input.addEventListener('input', ()=>{
    let x = event.target.value.replace(/\D/g, '').match(/(\d{0,1})(\d{0,3})(\d{0,3})(\d{0,2})(\d{0,2})/);
    event.target.value = !x[2] ? x[1] : '+' + x[1] + ' (' + x[2] + ') ' + x[3] + (x[4] ? '-' + x[4] : '') + (x[5] ? '-' + x[5] : '');
})

<input />

It works, but with one problem. When I press the backspace key, I erase the phone number to something like +1 (111). Such an entry is valid for the regular expression, and the string is replaced by itself

Answer 1

Per @ggorlen's suggestion in the comments, here is one way to do this:

let input = document.querySelector('input');

input.addEventListener('keydown', (event)=>{
    if (event.key === "Backspace" || event.key === "Delete") return;
    let x = event.target.value.replace(/\D/g, '').match(/(\d{0,1})(\d{0,3})(\d{0,3})(\d{0,2})(\d{0,2})/);
    event.target.value = !x[2] ? x[1] : '+' + x[1] + ' (' + x[2] + ') ' + x[3] + (x[4] ? '-' + x[4] : '') + (x[5] ? '-' + x[5] : '');
})

<input maxlength=18 />