Format currency input with 1000 separator and 2 decimal places upon typing using jQuery/JS?

Question

I have a text input where I want it to format while typing a value allowing 2 decimal places and 1000 separators. It should only allow digits. I have done the following but

Answer 1

You can limit the keys in the keydown event instead of keyup and allow specific keys to take effect, and then format the input on keyup event:

$("#testinput").on("keydown", function(e) {
  var keycode = (event.which) ? event.which : event.keyCode;
  if (e.shiftKey == true || e.ctrlKey == true) return false;
  if ([8, 110, 39, 37, 46].indexOf(keycode) >= 0 || // allow tab, dot, left and right arrows, delete keys
    (keycode == 190 && this.value.indexOf('.') === -1) || // allow dot if not exists in the value
    (keycode == 110 && this.value.indexOf('.') === -1) || // allow dot if not exists in the value
    (keycode >= 48 && keycode <= 57) || // allow numbers
    (keycode >= 96 && keycode <= 105)) { // allow numpad numbers
    // check for the decimals after dot and prevent any digits
    var parts = this.value.split('.');
    if (parts.length > 1 && // has decimals
      parts[1].length >= 2 && // should limit this
      (
        (keycode >= 48 && keycode <= 57) || (keycode >= 96 && keycode <= 105)
      ) // requested key is a digit
    ) {
      return false;
    } else {
      if (keycode == 110) {
        this.value += ".";
        return false;
      }
      return true;
    }
  } else {
    return false;
  }
}).on("keyup", function() {
  var parts = this.value.split('.');
  parts[0] = parts[0].replace(/,/g, '').replace(/^0+/g, '');
  if (parts[0] == "") parts[0] = "0";
  var calculated = parts[0].replace(/(\d)(?=(\d{3})+(?!\d))/g, "$1,");
  if (parts.length >= 2) calculated += "." + parts[1].substring(0, 2);
  this.value = calculated;
  if (this.value == "NaN" || this.value == "") this.value = 0;
});