Child Elements

<!DOCTYPE html>
<html>
<head>
<style>
div {
  border: 1px solid black;
  margin: 5px;
}
</style>
</head>
<body>

<p>Click the button to find out how many child nodes the div element below has.</p>

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

<div id="myDIV">
  <p>First p element (index 1)</p>
  <p>Second p element (index 3)</p>
</div>

<p><strong>Note:</strong> Whitespace inside elements is considered as text, and text 
is considered as nodes. In this example, index 0, 2 and 4 in DIV are text nodes.</p>

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

<script>
function myFunction() {
  var c = document.getElementById("myDIV").childNodes.length;
  document.getElementById("demo").innerHTML = c;
}
</script>

</body>
</html>