Forcing form text to be lower-case

Question

How could I force the text in the \"username\" text input to be lower-case regardless of what user types?

Answer 1

setInterval() will run if the user pastes something in

setInterval(function(){
  let myinput = document.getElementById('myinput');
  //make lowercase
  myinput.value = myinput.value.toString().toLowerCase();
  //remove spaces (if you want)
  myinput.value = myinput.value.toString().replace(' ', '');
  //force specific characters
  myinput.value = myinput.value.toString().replace(/[^a-z0-9\/\-_]/, '');
}, 10);

because this is a loop function using .replace(), replacing only first occurrence at a time, but still looping all of them, this appears to animate removing spaces on pasted text.