How to do date masking using javascript (without JQuery)?

Answer 1

I had some trouble getting the currently accepted answers to work properly while retaining the ability to backspace. This was my solution. It retains backspacing and also doesn't show the slash until the number following it is typed.

const maskDate = value => {
  let v = value.replace(/\D/g,'').slice(0, 10);
  if (v.length >= 5) {
    return `${v.slice(0,2)}/${v.slice(2,4)}/${v.slice(4)}`;
  }
  else if (v.length >= 3) {
    return `${v.slice(0,2)}/${v.slice(2)}`;
  }
  return v
}

I've also create a github gist for this snippet here.