JSFiddle - React, Tailwind, and code Playground

HTML

<span class="someClass position1" >span1</span>
<span class="someClass" >span2</span>
<span class="someClass" >span3</span>
<span class="someClass position2" >span4</span>
<span class="someClass" >span5</span>
<span class="someClass position4" >span6</span>
<span class="someClass position10" >span7</span>
<span class="someClass" >span8</span>
<span class="someClass position12" >span9</span>

JavaScript

$(".someClass").each(function(){
    var classes = $(this).attr('class').split(/\s+/);
    for (var i = 0; i < classes.length; ++i)
    {
        if (classes[i].match(/^position\d+$/i)) {
            $(this).css('background-color', 'red');
        }
    }
});