es6基础(5)--数值扩展

 1 {    
 2     //Number.isFinite数字是有尽的
 3     console.log(Number.isFinite(15));//true
 4     console.log(Number.isFinite(NaN));//false
 5     console.log(Number.isFinite(‘true‘/0));//false
 6     console.log(Number.isNaN(NaN));//true
 7     console.log(Number.isNaN(10));//false
 8 }
 9 {
10     //判断是否为整数,括号里面必须是数字
11     console.log(‘25‘,Number.isInteger(25));//true
12     console.log(‘25.0‘,Number.isInteger(25.0));//true
13     console.log(‘25.1‘,Number.isInteger(25.1));//false
14     console.log(‘25‘,Number.isInteger(‘25‘));//false
15 }
16 {
17     //向下取整
18     console.log(4.1,Math.trunc(4.1));//4
19     console.log(4.9,Math.trunc(4.9));//4
20 }
21 {
22     //判断正数负数0，返回-1则为负数，0就是0,1为正数，NaN就是非数字
23     console.log(‘-5‘,Math.sign(-5));//-1
24     console.log(‘0‘,Math.sign(0));//0
25     console.log(‘5‘,Math.sign(5));//1
26     console.log(‘fff‘,Math.sign(‘fff‘));//NaN
27 }