ES6数值扩展

　　　// Number.EPSILON 是js表示的最小精度

            console.log(0.1 + 0.2)

            function equal (a, b) {

                if (Math.abs(a-b) < Number.EPSILON) {

                    return true

                } else {

                    return false

                }

            }

            console.log(0.1 + 0.2 === 0.3) // false

            console.log(equal(0.1 + 0.2, 0.3)) // true

            // 检测一个数是否是有限数 Number.isFinite

           console.log( Number.isFinite(100)) // true

           console.log( Number.isFinite(100 / 0)) // false

            // 检测一个数是不是NAN

            console.log(Number.isNaN(123)) // false

            // Number.parseInt()转成整数

            console.log(Number.parseInt('521iloveyou')) // 521

           // Number.parseFloat()转成浮点数

           console.log(Number.parseFloat('3.2121221神奇'))// 3.2121221

           // 判断一个数是否是整数

           console.log(Number.isInteger(5)) // true

           console.log(Number.isInteger(2.5)) // false

           // 把小数部分抹掉

           console.log(Math.trunc(3.5)) // 3

           // 判断一个数是整数，负数还是0

           console.log(Math.sign(100)) // 1

           console.log(Math.sign(0))   // 0

           console.log(Math.sign(-100)) // -1