JSFiddle - React, Tailwind, and code Playground

HTML

<div class="blue-highlight datepick-other-month">1</div>
<div class="blue-highlight datepick-other-month">2</div>
<div class="blue-highlight datepick-other-month">3</div>
<div class="blue-highlight datepick-other-month">4</div>
<div class="blue-highlight datepick-other-month">5</div>

JavaScript

var elems = $("*[class*='-highlight datepick-other-month']");

elems.attr('class', function(_, old){
    return $.grep(old.split(/ +/), function(v){
         return !v.match(/-highlight$/);
    }).join(' ');
})