新增digit数字计算工具

src/utils/digit.ts

@@ -0,0 +1,165 @@
+let _boundaryCheckingState = true // 是否进行越界检查的全局开关
+
+/**
+ * 把错误的数据转正
+ * @private
+ * @example strip(0.09999999999999998)=0.1
+ */
+function strip(num: number | string, precision = 15) {
+  return +parseFloat(Number(num).toPrecision(precision))
+}
+
+/**
+ * Return digits length of a number
+ * @private
+ * @param {*number} num Input number
+ */
+function digitLength(num: number | string) {
+  // Get digit length of e
+  const eSplit = num.toString().split(/[eE]/)
+  const len = (eSplit[0].split('.')[1] || '').length - +(eSplit[1] || 0)
+  return len > 0 ? len : 0
+}
+
+/**
+ * 把小数转成整数,如果是小数则放大成整数
+ * @private
+ * @param {*number} num 输入数
+ */
+function float2Fixed(num: number | string) {
+  if (num.toString().indexOf('e') === -1) {
+    return Number(num.toString().replace('.', ''))
+  }
+  const dLen = digitLength(num)
+  return dLen > 0 ? strip(Number(num) * Math.pow(10, dLen)) : Number(num)
+}
+
+/**
+ * 检测数字是否越界，如果越界给出提示
+ * @private
+ * @param {*number} num 输入数
+ */
+function checkBoundary(num: number | string) {
+  if (_boundaryCheckingState) {
+    if (num > Number.MAX_SAFE_INTEGER || num < Number.MIN_SAFE_INTEGER) {
+      window.console.warn(`${num} 超出了精度限制，结果可能不正确`)
+    }
+  }
+}
+
+/**
+ * 把递归操作扁平迭代化
+ * @param {number[]} arr 要操作的数字数组
+ * @param {function} operation 迭代操作
+ * @private
+ */
+function iteratorOperation(arr: number[], operation: Function) {
+  const [num1, num2, ...others] = arr
+  let res = operation(num1, num2)
+
+  others.forEach((num) => {
+    res = operation(res, num)
+  })
+
+  return res
+}
+
+/**
+ * 高精度乘法
+ * @export
+ */
+export function times(...nums: any) {
+  if (nums.length > 2) {
+    return iteratorOperation(nums, times)
+  }
+
+  const [num1, num2] = nums
+  const num1Changed = float2Fixed(num1)
+  const num2Changed = float2Fixed(num2)
+  const baseNum = digitLength(num1) + digitLength(num2)
+  const leftValue = num1Changed * num2Changed
+
+  checkBoundary(leftValue)
+
+  return leftValue / Math.pow(10, baseNum)
+}
+
+/**
+ * 高精度加法
+ * @export
+ */
+export function plus(...nums: any) {
+  if (nums.length > 2) {
+    return iteratorOperation(nums, plus)
+  }
+
+  const [num1, num2] = nums
+  // 取最大的小数位
+  const baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)))
+  // 把小数都转为整数然后再计算
+  return (times(num1, baseNum) + times(num2, baseNum)) / baseNum
+}
+
+/**
+ * 高精度减法
+ * @export
+ */
+export function minus(...nums: any) {
+  if (nums.length > 2) {
+    return iteratorOperation(nums, minus)
+  }
+
+  const [num1, num2] = nums
+  const baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)))
+  return (times(num1, baseNum) - times(num2, baseNum)) / baseNum
+}
+
+/**
+ * 高精度除法
+ * @export
+ */
+export function divide(...nums: any) {
+  if (nums.length > 2) {
+    return iteratorOperation(nums, divide)
+  }
+
+  const [num1, num2] = nums
+  const num1Changed = float2Fixed(num1)
+  const num2Changed = float2Fixed(num2)
+  checkBoundary(num1Changed)
+  checkBoundary(num2Changed)
+  // 重要，这里必须用strip进行修正
+  return times(num1Changed / num2Changed, strip(Math.pow(10, digitLength(num2) - digitLength(num1))))
+}
+
+/**
+ * 四舍五入
+ * @export
+ */
+export function round(num: number, ratio: number) {
+  const base = Math.pow(10, ratio)
+  let result = divide(Math.round(Math.abs(times(num, base))), base)
+  if (num < 0 && result !== 0) {
+    result = times(result, -1)
+  }
+  // 位数不足则补0
+  return result
+}
+
+/**
+ * 是否进行边界检查，默认开启
+ * @param flag 标记开关，true 为开启，false 为关闭，默认为 true
+ * @export
+ */
+export function enableBoundaryChecking(flag = true) {
+  _boundaryCheckingState = flag
+}
+
+export default {
+  times,
+  plus,
+  minus,
+  divide,
+  round,
+  enableBoundaryChecking,
+}