Changing the keypress

Question

In an input box or contenteditable=true div, how can I modify a keypress for the letter \"a\" to return a keybress for the letter \"b\"? I.e., every time you type the letter

Answer 1

My solution example (change in input[type=text] the character ',' to '.'):

element.addEventListener('keydown', function (event) {
if(event.key === ','){
  setTimeout(function() {
    event.target.value += '.';
  }, 4);
  event.preventDefault();
};