js中针对toFixed 的精度调整

 1 /* eslint-disable-next-line */
 2 Number.prototype.toFixed = function(d) {
 3   let s = `${this}`
 4   /* eslint-disable-next-line */
 5   if (!d) d = 0
 6   if (s.indexOf(".") === -1) s += "."
 7   s += new Array(d + 1).join("0")
 8   if (new RegExp(`^(-|\\+)?(\\d+(\\.\\d{0,${d + 1}})?)\\d*$`).test(s)) {
 9     s = `0${RegExp.$2}`
10     const pm = RegExp.$1
11     let a = RegExp.$3.length
12     let b = true
13     if (a === d + 2) {
14       a = s.match(/\d/g)
15       if (parseInt(a[a.length - 1], 10) > 4) {
16         for (let i = a.length - 2; i >= 0; i--) {
17           a[i] = parseInt(a[i], 10) + 1
18           if (a[i] === 10) {
19             a[i] = 0
20             b = i !== 1
21           } else break
22         }
23       }
24       s = a.join("").replace(new RegExp(`(\\d+)(\\d{${d}})\\d$`), "$1.$2")
25     }
26     if (b) s = s.substr(1)
27     return (pm + s).replace(/\.$/, "")
28   }
29   return `${this}`
30 }