1.点击切换颜色:
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> <style> .my{ background-color: red; width: 100px; height: 100px; } </style> </head> <body> <div class = "my"></div> <script> var flag = true; var oMy = document.getElementsByClassName("my")[0] oMy.onclick = function(){ if (flag){ oMy.style.backgroundColor = 'green'; flag = false; }else{ oMy.style.backgroundColor = 'red'; flag = true; } } </script> </body> </html>