<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
  $(".btn1").click(function(){
    $("p").slideUp();
  });
  $(".btn2").click(function(){
    $("p").slideDown();
  });
  $(".btn3").click(function(){
    if ($("p").css("display") != "none")
    alert("Element visible");
    else 
    alert("Element hidden");
  });
});
</script>
</head>
<body>

<p>This is a paragraph.</p>

<button class="btn1">Slide up</button>
<button class="btn2">Slide down</button>
<button class="btn3">Check</button>

</body>
</html>

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.