12-2 js基础

一数据类型

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <title>数据类型</title>
 6 </head>
 7 <body>
 8 <script>
 9 
10     var a=123;
11     console.log(typeof a);
12     //string
13     var b='123';
14     console.log(typeof b);
15     //boolean
16     var c=false;
17     console.log(typeof c);
18     //null
19     var d=null;
20     console.log(d);
21     //undefined未定义
22      var d1;
23      console.log(typeof d1)
24 
25 </script>
26 
27 </body>
28 </html>

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