<!DOCTYPE html>
<html>
<head>
<style>
div {
border: 1px solid black;
margin: 5px;
}
</style>
</head>
<body>
<div class="example">
<p>P element in first div with class="example". Div's index is 0.</p>
</div>
<div class="example color">
<p>P element in first div with class="example color". Div's index is 0.</p>
</div>
<div class="example color">
<p>P element in second div with class="example color". Div's index is 1.</p>
</div>
<p>Click the button to change the background color of the first div element with the classes "example" and "color".</p>
<button onclick="myFunction()">Try it</button>
<p><strong>Note:</strong> The getElementsByClassName() method is not supported in Internet Explorer 8 and earlier versions.</p>
<script>
function myFunction() {
var x = document.getElementsByClassName("example color");
x[0].style.backgroundColor = "red";
}
</script>
</body>
</html>