0093 numeric Number: integer, decimal, hexadecimal numeric, numeric range, three specific numeric value

JavaScript can both save integer numeric types, you can also save a decimal (floating point).

var age = 21;       // 整数
var Age = 21.3747;  // 小数     

1. Numeric hexadecimal

   The most common band have binary, octal, decimal, hexadecimal.

     // 1.八进制数字序列范围：0~7
    var num1 = 07;   // 对应十进制的7
    var num2 = 019;  // 对应十进制的19
    var num3 = 08;   // 对应十进制的8
     // 2.十六进制数字序列范围：0~9以及A~F
    var num = 0xA;   

   At present, we only need to remember that in JS octal preceded by 0, hexadecimal preceded by 0x

2. Numeric range

   The maximum and minimum values ​​in JavaScript

   • Maximum: Number.MAX_VALUE, this value: 1.7976931348623157e + 308

   • Minimum: Number.MIN_VALUE, this value: 5e-32

3. Three special numeric value

   • Infinity, represents the infinite, greater than any value

   • -Infinity, on behalf of the infinitesimal, less than any value

   • NaN, Not a number, representing a non-numeric

4. isNaN

   It used to determine whether a variable is non-numeric type, returns true or false

js var usrAge = 21; var isOk = isNaN(userAge); console.log(isNum); // false ，21 不是一个非数字 var usrName = "andy"; console.log(isNaN(userName));// true ，"andy"是一个非数字