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<!DOCTYPE html> <html> <body> <p>当您输入输入字段（FORM 的子）时，会触发一个将背景颜色设置为黄色的函数。当您离开输入字段时，会触发一个删除背景颜色的函数。</p> <form id="myForm"> <input type="text" id="myInput"> </form> <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>