<!DOCTYPE html>
<html>
<head>
<style>
#myDIV {
  border: 1px solid black;
}
</style>
</head>
<body>

<div id="myDIV">
  <p>I am a p element inside div, and I have a <span id="mySPAN"><b>span</b></span> element inside of me.</p>
</div>

<span id="mySPAN2"><b>span</b></span>
<p>Click the button to find out if the div element contains a span element.</p>

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {
  var span = document.getElementById("mySPAN");
  var div = document.getElementById("myDIV").contains(span);
  window.alert(div);
}
</script>

</body>
</html>