5.6.2 Number 类型

Number 类型提供了一些用于将数值格式化为字符串的方法

toFixed()

按照指定小数位返回，若本身小数位多，剩余位进行舍入

let num = 10;
console.log(num.toFixed(2)); //10.00
let num2 = 10.005;
console.log(num2.toFixed(2)); //10.01

未传参时，返回整数

let num = 10;
console.log(num.toFixed()); //10
let num2 = 10.005;
console.log(num2.toFixed()); //10

toExponential()

返回指数表示法，同样接收表示位数的参数

let num = 10;
console.log(num.toExponential(1)); //1.0e+1
let num2 = 10.005;
console.log(num2.toExponential(1)); //1.0e+1

toPrecision()

自行选择调用toFixed()还是toExponential()
接收的参数表示所有数字的位数

let num = 99;
console.log(num.toPrecision(1)); //1e+2
console.log(num.toPrecision(2)); //99
console.log(num.toPrecision(3)); //99.0