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<!DOCTYPE html> <html> <head> <style> #myDIV { border: 1px solid black; margin: 5px; } </style> </head> <body> <div id="myDIV"> <h2 class="example">A heading with class="example" in div</h2> <p class="example">A p element with class="example" in a div.</p> <p class="example">Another p element with class="example" in a div.</p> <p>A p element in div with a <span class="example">span element with class="example"</span> inside of it.</p> </div> <p>Click the button to add a background color to all elements with class="example" inside DIV.</p> <button onclick="myFunction()">Try it</button> <p><strong>Note:</strong> The querySelectorAll() method is not supported in Internet Explorer 8 and earlier versions.</p> <script> function myFunction() { var x = document.getElementById("myDIV").querySelectorAll(".example"); var i; for (i = 0; i < x.length; i++) { x[i].style.backgroundColor = "red"; } } </script> </body> </html>