JSFiddle - React, Tailwind, and code Playground

JavaScript

var regexp = /^((?=[a-z \']).)+$/i;
    
    var val1 = "Normal Text' Compromised";
    var val2 = "UTF Text' Połącz Słońce w Mózu";
    var val3 = "Illegal char: Blac & White";
    
    document.write( '1:' + regexp.test( val1 ) + "<br>" );
    document.write( '2:' + regexp.test( val2 ) + "<br>" );
    document.write( '4:' + regexp.test( val3 ) + "<br>" );