菜鸟学堂
在线运行
源代码
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>菜鸟学堂()</title> </head> <body> <p id="demo"></p> <script> document.getElementById("demo").innerHTML = typeof undefined + "<br>" + typeof null + "<br>" + (null === undefined) + "<br>" + (null == undefined); </script> </body> </html>
运行结果
在线运行
菜鸟学堂 edu.jb51.net