JSFiddle - React, Tailwind, and code Playground

HTML

<div id="marqueurs">
    <div class="marqueur">
        <p>Points à récupérer : <span class="pointsXP">10</span></p>
        <button class="recupererXP">Récupérer</button>
    </div>
    <br/>
    <div class="marqueur">
        <p>Points à récupérer : <span class="pointsXP">5</span></p>
        <button class="recupererXP">Récupérer</button>
    </div>
</div>
<p>Points cumulés : <span id="totalXP">2</span></p>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

JavaScript

$(document).ready(function() {
    var currentXP = $("#totalXP").text();
    $(".recupererXP").click(function() {
        var value = $(".pointsXP").text();                                
        var newValue = parseInt(value) + parseInt(currentXP);                                  
        $('#totalXP').text(newValue);
    });
});