JavaScript--数据类型转换

数字转字符串与字符串转数字

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <title>Title</title>
 6 </head>
 7 <body>
 8 
 9 </body>
10 </html>
11 <script>
12     var num = 5;
13     console.log(num.toString()); // "5"
14     console.log(String(num));  //"5"
15     var num = 0;
16     console.log(num.toString()); //"0"
17     console.log(String(num));   //"0"
18 
19     var num = null;
20     console.log(String(null)); // "null"
21     console.log(typeof String(null)); // string
22 
23     var num = "8000dafdasdfa";
24     console.log(Number(num)); //NaN
25     console.log(typeof  Number(num)); //number
26 
27     var num1 = "0.0823.123aaa123";
28     console.log(Number(num1)); // NaN
29     console.log(parseInt(num1)); //0
30     console.log(parseFloat(num1)); //0.0823
31 
32     //parseInt() 强制转换成数值整数型，不会四舍五入
33     //parseFloat() 会解析第一个，遇到第二个、或者非数字结束
34 </script>