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

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

Answer 2

The property event.key gave me an undefined value. Instead, I used event.keyCode:

function alphaOnly(event) {   var key = event.keyCode;   return ((key >= 65 && key <= 90) || key == 8); }; 

Note that the value of 8 is for the backspace key.