Event delegation: using the focusin event. This is not supported by Firefox.
When you enter the input field, a function is triggered which sets the background color to yellow.
When you leave the input field, a function is triggered which removes the background color.</p>
<!DOCTYPE html> <html> <body> <form id="myForm"> <input type="text" id="myInput"> </form>// w ww .ja v a 2 s .com <script> var x = document.getElementById("myForm"); x.addEventListener("focusin", myFocusFunction); x.addEventListener("focusout", myBlurFunction); function myFocusFunction() { document.getElementById("myInput").style.backgroundColor = "yellow"; } function myBlurFunction() { document.getElementById("myInput").style.backgroundColor = ""; } </script> </body> </html>