<button onClick="openPopup('div1');">open div1</button>
<div id="div1" class="popup" style="display:none;">
This is a test message div1
<div class="cancel" onclick="closePopup();"></div>
</div>
<button onClick="openPopup('div2');">open div2</button>
<div id="div2" class="popup" style="display:none;">
This is a test message div2
<div class="cancel" onclick="closePopup();"></div>
</div>