Number 小数点精度问题解决方案

var floatCalc = function (a, b) {
    a = a + '', b = b + '';
    var aNum = a.indexOf('.'),
        bNum = b.indexOf('.'),
        aSum,
        bSum,
        resultNum,
        inta,
        intb;
    aSum = aNum < 0 ? 0 : a.split('.')[1].length;
    bSum = bNum < 0 ? 0 : b.split('.')[1].length;
    resultNum = aSum > bSum ? aSum : bSum;
    inta = aNum < 0 ? Number(a + (Math.pow(10, resultNum) + '').replace('1', '')) : (function () {
        a = a.replace('.', '');
        a = resultNum == aSum ? a : a + (Math.pow(10, resultNum - aSum) + '').replace('1', '');
        return Number(a);
    }())
    intb = bNum < 0 ? Number(b + (Math.pow(10, resultNum) + '').replace('1', '')) : (function () {
        b = b.replace('.', '');
        b = resultNum == bSum ? b : b + (Math.pow(10, resultNum - bSum) + '').replace('1', '');
        return Number(b);
    }())
    return {
        a: inta,
        b: intb,
        num: resultNum
    };
}
const _Number: any = Number;
//加法
_Number.prototype.add = function (n) {
    var o = floatCalc(this, n);
    return (o.a + o.b) / Math.pow(10, o.num);
}
//减法
_Number.prototype.minus = function (n) {
    var o = floatCalc(this, n);
    return (o.a - o.b) / Math.pow(10, o.num);
}
//乘法
_Number.prototype.subtract = function (n) {
    var o = floatCalc(this, n);
    return (o.a * o.b) / Math.pow(10, o.num * 2);
}
//除法
_Number.prototype.divide = function (n) {
    var o = floatCalc(this, n);
    return (o.a / o.b);
}

var floatCalc = function (a: (number | string), b: (string | number)) {
  a = a + '', b = b + '';
  var aNum = a.indexOf('.'),
    bNum = b.indexOf('.'),
    aSum,
    bSum,
    resultNum,
    inta,
    intb;
  aSum = aNum < 0 ? 0 : a.split('.')[1].length;
  bSum = bNum < 0 ? 0 : b.split('.')[1].length;
  resultNum = aSum > bSum ? aSum : bSum;
  inta = aNum < 0 ? Number(a + (Math.pow(10, resultNum) + '').replace('1', '')) : (function () {
    a = a.replace('.', '');
    a = resultNum == aSum ? a : a + (Math.pow(10, resultNum - aSum) + '').replace('1', '');
    return Number(a);
  }())
  intb = bNum < 0 ? Number(b + (Math.pow(10, resultNum) + '').replace('1', '')) : (function () {
    b = b.replace('.', '');
    b = resultNum == bSum ? b : b + (Math.pow(10, resultNum - bSum) + '').replace('1', '');
    return Number(b);
  }())
  return {
    a: inta,
    b: intb,
    num: resultNum
  };
}
const _Number: any = Number;
//加法
export const add = function (a: number, b: number) {
  var o = floatCalc(a, b);
  return (o.a + o.b) / Math.pow(10, o.num);
}
//减法
export const minus = function (a: number, b: number) {
  var o = floatCalc(a, b);
  return (o.a - o.b) / Math.pow(10, o.num);
}
//乘法
export const subtract = function (a: number, b: number) {
  var o = floatCalc(a, b);
  return (o.a * o.b) / Math.pow(10, o.num * 2);
}
//除法
export const divide = function (a: number, b: number) {
  var o = floatCalc(a, b);
  return (o.a / o.b);
}