alert the buttons text //source https://jsbin.com/fawepetaha

index.html

<div class="btns">
    <p>Write JavaScript (using jQuery is fine) so that clicking on any button will cause an alert to popup with the text of the button that was clicked.</p>

    <p>Make sure your solution is as efficient as possible even if there are a lot more <code>button.btn</code>'s added on the page.  Do not use unnecessary event listeners.</p>
  
    <button class="btn">c</button>
    <button class="btn">l</button>
    <button class="btn">o</button>
    <button class="btn">s</button>
    <button class="btn">e</button>
    <button class="btn">.</button>
    <button class="btn">i</button>
    <button class="btn">o</button>
</div>

<script src="https://code.jquery.com/jquery-2.1.4.js"></script>
<script id="jsbin-javascript">
// Will even work with buttons inserted after page rendering completed. ;)
$('div.btns').mouseup(function(e){
    $(e.target).is('button.btn') && alert(e.target.innerText);
});
</script>