JSFiddle - React, Tailwind, and code Playground

HTML

<form>
<input type="checkbox" name="vehicle" value="a" class="checked" /> Apple<br />
<input type="checkbox" name="vehicle" value="b" /> Banana<br />
<input type="checkbox" name="vehicle" value="c" /> Carrot<br />
<input type="checkbox" name="vehicle" value="d" class="checked" /> Dill Pickel<br />

</form>

JavaScript

$(document).ready(function() {
    $('form input[type="checkbox"]').each(function (){
        if($(this).hasClass('checked')){
            $(this).attr('checked', true);
        }
    });
});