JSFiddle - React, Tailwind, and code Playground

HTML

<div class="rating">
<a href="#" data-value="1" data-target="#numb">↑</a>
<a href="#" data-value="-1" data-target="#numb">↓</a>
<span id="numb">37</span>
</div>

CSS

a {text-decoration:none;}
.blue { color: #00f }
.red { color: #f00 }

JavaScript

$(function(){
    $(document.body).on('click', '[data-value][data-target]', function(){
        var target = $($(this).data('target'));
        var value = $(this).data('value');
        
        target.text(+target.text() + value).toggleClass("red", value < 0).toggleClass("blue", value > 0);
    });
});