Javascript DOM HTML Element getElementsByClassName() Method by class name for <div>

Introduction

Change the background color of all elements with class="child" inside of a <div> element:

Click the button to add a background color to all elements with class="child" inside the div element with id="myDIV".

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<!DOCTYPE html>
<html>
<head>
<style>
div {/*  ww  w.  j  a v a 2s.  c  o  m*/
  border: 1px solid black;
  margin: 5px;
}
</style>
</head>
<body>

<div id="myDIV">
  <p class="child">A p element with class="child" in a div.</p>
  <p class="child">Another p element with class="child" in a div.</p>
  <p>A p element in div with a <span class="child">
  span element with class="child"</span> inside of it.</p>
</div>
<button onclick="myFunction()">Test</button>
<script>
function myFunction() {
  var x = document.getElementById("myDIV");
  var y = x.getElementsByClassName("child");
  var i;
  for (i = 0; i < y.length; i++) {
    y[i].style.backgroundColor = "red";
  }
}
</script>
</body>
</html>



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