事件：
1、注册事件
a. <div onxxxx=””></div>
b. document .onxxxx= function() //找到这个标签
2、this，触发当前事件的标签
3、event ，触发当前标签的事件内容
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <div onmouseover="Func(this)" onmouseout="Func1(this)"> 123</div> <input type="text" onkeydown="Down(this,event);"> <script> function Down(ths,e) { console.log(e.keyCode); } function Func(ths) { ths.style.color = 'red'; } function Func1(ths) { ths.style.color = 'black'; } function </script> </body> </html>