How to force input to only allow Alpha Letters?

Question

using jQuery here, however unable to prevent numbers from being typed into the input field

http://codepen.io/leongaban/pen/owbjg

Input

<input type="text" name="field" maxlength="8"
    title="Only Letters"
    value="Type Letters Only"
    onkeydown="return alphaOnly(event);"
    onblur="if (this.value == '') {this.value = 'Type Letters Only';}"
    onfocus="if (this.value == 'Type Letters Only') {this.value = '';}"/>

jQuery

function alphaOnly(event) {

  alert(event);

  var key;

  if (window.event) {
    key = window.event.key;
  } else if (e) {
    key = e.which;
  }
  //var key = window.event.key || event.key;
  alert(key.value);
  return ((key >= 65 && key <= 90) || (key >= 95 && key <= 122));

}

I've seen plenty of examples here on how to restrict to only Numbers, and I'm using the correct key codes for a-z and A-Z. Do you see what I'm doing wrong?

Answer 1

Short ONELINER:

<input onkeypress="return /[a-z]/i.test(event.key)" >

For all unicode letters try this regexp: /\p{L}/u (but ... this) - and here is working example :)