<section>
    <button class="changeDiv" id="Button_1">1</button>
    <button class="changeDiv" id="Button_2">2</button>
    <button class="changeDiv" id="Button_3">3</button>
    <button class="changeDiv" id="Button_4">4</button>

    <script>

        var buttons = document.getElementsByClassName("changeDiv");
        for (var i = 0; i < buttons.length; i++) {
            buttons[i].addEventListener("click", function(){ alert('cliked' + buttons[i].id); });
            alert('Loaded' + buttons[i].id);
        }

    </script>
</section>