JSFiddle - React, Tailwind, and code Playground

HTML

<select id="selName" class='optional'>
    <option value="bob">Bob Carter</option>
    <option value="fred">Fred Flintstone</option>
</select>
<select id="selCar" class='require_one'>
    <option value="mustang">Mustang</option>
    <option value="a8">Audi A8</option>
</select>
<select id="selHouse" class='require_one'>
    <option value="blue">Blue house</option>
    <option value="white">1600 Penn</option>
</select>
<select id="selCountry" class='require_one'>
    <option value="usa">USA</option>
    <option value="mex">Mexico</option>
</select>
<input id="mySubmit" type="button" value="Submit">

JavaScript

$('#mySubmit').attr('disabled','disabled');

$('select').change(function(){
    if ( $(this).hasClass('require_one') ){
        $('#mySubmit').removeAttr('disabled');
    }
});

$('#mySubmit').click(function() {
   $('#myFormID').submit(); 
});