! DOCTYPE html html lang ="en" head meta charset ="UTF-8" title Document / title / head body input type ="button" value ="按钮" id ="btn" script var btn = document.getElementById( ‘ btn ‘ ); // 第一个参数，事件的名称前要加
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> </head> <body> <input type="button" value="按钮" id="btn"> <script> var btn = document.getElementById(‘btn‘); // 第一个参数，事件的名称前要加 on btn.attachEvent(‘onclick‘, function () { alert(‘hello world‘); }); btn.attachEvent(‘onclick‘, function () { alert(‘hello itheima‘); }); </script> </body> </html>