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" data-min="35" data-max="39">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');
        var current = +target.text();
        var next = current  + value;
        
        if(target.data('min') <= next  && target.data('max') >= next)
            target.text(next).toggleClass("red", value < 0).toggleClass("blue", value > 0);
    });
});