小数乘法精确率处理

问题：

let str = '2.53';
let num = parseFloat(str) *100;

alert(num) -> 252.999999999

解决：

let str = '2.53'
let num = parseFloat(str *100).toFixed(2)
let num1 = parseFloat(str *100).toFixed(0)

alert(num) -> 253.00
alert(num1) -> 253