JSFiddle - React, Tailwind, and code Playground

by Ganesh

HTML

<input type="text" id="city_field" />

<div class="r_validation"></div>

JavaScript

var r = /^[a-zA-ZäöüÄÖÜ]+$/;

console.log(r.test('Foo'));
console.log(r.test('Foo123'));
console.log(r.test('foo,'));
console.log(r.test('foo, '));
console.log(r.test('foo '));

$(function(){

    $("#city_field").bind("keyup",
       function(event){ 
          var  regex = /^[a-zA-ZäöüÄÖÜ]+$/;
          if (regex.test($("#city_field").val())) {  
              $('.r_validation').html('valid');
          } else {  
              $('.r_validation').html("FAIL");
          }
    });
});