JSFiddle - React, Tailwind, and code Playground

HTML

<fieldset id="cont">
    <div id="top">
        <input type="text" class="required"  />
        <input type="text" id="bar"  />
    </div>
    <div id="btm">
        <input type="text" class="required2"  />
        <input type="text" id="foo"  />
    </div>
</fieldset>

JavaScript

var selector = ".required,#bar",
    selector2 = "#btm :input",
    container = "#cont";
        
alert($(container).find(selector).length); // FF,IE,Webkit: alerts 2, Opera alerts 2
alert($(container).find(selector + "," + selector2).length); // FF,IE,Webkit: alerts 4, Opera alerts 2
alert($(container).find(selector2 + "," + selector).length); // FF,IE,Webkit: alerts 4, Opera alerts 4