<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Document</title> </head> <body> <script> // null 也是一种js的数据类型 表示空值 var a = null; console.log(a); </script> </body> </html>
