SO fiddle

Test Fiddle mainly for SO Questions

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/dot-luv/jquery-ui.css">
Type something here: <input type="text" id="in">

<div id="out"></div>

JavaScript

var $out = $("#out");
$("input").keyup(function () {
    if (/^[a-zA-Z '-]+$/.test(this.value))
        $out.text("Regex tested OK");
    else
        $out.text("Regex tested not OK");
});