【转】JS中处理Number浮点数精度问题

https://github.com/dt-fe/number-precision

~(function(root, factory) {
  if (typeof define === "function" && define.amd) {
    define([], factory);
  } else if (typeof module === "object" && module.exports) {
    module.exports = factory();
  } else {
    root.NP = factory();
  }
}(this, function() {
  'use strict';
    /**
     * @ file 解决浮动运算问题，避免小数点后产生多位数和计算精度损失。
     * 问题示例：2.3 + 2.4 = 4.699999999999999，1.0 - 0.9 = 0.09999999999999998
     */
    return {
            /**
             * 把错误的数据转正
             * strip(0.09999999999999998)=0.1
             */
            strip: function (num, precision = 12) {
              return +parseFloat(num.toPrecision(precision));
            },
            /**
             * Return digits length of a number
             * @ param {*number} num Input number
             */
            digitLength: function (num) {
              // 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;
            },
            /**
             * 精确加法
             */
            plus: function (num1, num2) {
              const baseNum = Math.pow(10, Math.max(this.digitLength(num1), this.digitLength(num2)));
              return (num1 * baseNum + num2 * baseNum) / baseNum;
            },
            /**
             * 精确减法
             */
            minus: function (num1, num2) {
              const baseNum = Math.pow(10, Math.max(this.digitLength(num1), this.digitLength(num2)));
              return (num1 * baseNum - num2 * baseNum) / baseNum;
            },
            /**
             * 精确乘法
             */
            times: function (num1, num2) {
              const num1Changed = Number(num1.toString().replace('.', ''));
              const num2Changed = Number(num2.toString().replace('.', ''));
              const baseNum = this.digitLength(num1) + this.digitLength(num2);
              return num1Changed * num2Changed / Math.pow(10, baseNum);
            },
            /**
             * 精确除法
             */
            divide: function (num1, num2) {
              const num1Changed = Number(num1.toString().replace('.', ''));
              const num2Changed = Number(num2.toString().replace('.', ''));
              return this.times((num1Changed / num2Changed), Math.pow(10, this.digitLength(num2) - this.digitLength(num1)));
            },
            /**
             * 四舍五入
             */
            round: function (num, ratio) {
              const base = Math.pow(10, ratio);
              return this.divide(Math.round(this.times(num, base)), base);
            }
      };
}));

方法：
NP.strip(num)         // strip a number to nearest right number
NP.plus(num1, num2)   // addition, num + num2
NP.minus(num1, num2)  // subtraction, num1 - num2
NP.times(num1, num2)  // multiplication, num1 * num2
NP.divide(num1, num2) // division, num1 / num2
NP.round(num, ratio)  // round a number based on ratio

使用：

NP.strip(0.09999999999999998); // =0.1
NP.plus(0.1, 0.2);             // =0.3 not 0.30000000000000004
NP.plus(2.3, 2.4);             // =4.7 not 4.699999999999999
NP.minus(1.0, 0.9);            // =0.1 not 0.09999999999999998
NP.times(3, 0.3);              // =0.9 not 0.8999999999999999
NP.times(0.362, 100);          // = 36.2, not 36.199999999999996
NP.divide(1.21, 1.1);          // =1.1 not 1.0999999999999999
NP.round(0.105, 2);            // =0.11 not 0.1