解决浮运算问题

/*js浮点数运算问题解决办法
   @params type: 1乘法，2除法 3减法，4加法
   @params arg1 arg2 按照表达式顺序来
   */

  floatCalculation(arg1, arg2, type) {
    if (type == 1) {
      let m = 0,
        s1 = arg1.toString(),
        s2 = arg2.toString();
      try {
        m += s1.split(".")[1].length
      } catch (e) {
        console.log(e)
      }
      try {
        m += s2.split(".")[1].length
      } catch (e) {
        console.log(e)
      }
      return Number(s1.replace(".", "")) * Number(s2.replace(".", "")) / Math.pow(10, m);
    } else if (type == 2) {
      let t1 = 0,
        t2 = 0,
        r1, r2;
      try {
        t1 = arg1.toString().split(".")[1].length
      } catch (e) {
        console.log(e)
      }
      try {
        t2 = arg2.toString().split(".")[1].length
      } catch (e) {
        console.log(e)
      }
      r1 = Number(arg1.toString().replace(".", ""));
      r2 = Number(arg2.toString().replace(".", ""));
      return (r1 / r2) * Math.pow(10, t2 - t1);
    } else if (type == 3) {
      let r1, r2, m, n;
      try {
        r1 = arg1.toString().split(".")[1].length
      } catch (e) {
        r1 = 0
      }
      try {
        r2 = arg2.toString().split(".")[1].length
      } catch (e) {
        r2 = 0
      }
      m = Math.pow(10, Math.max(r1, r2));
      //last modify by deeka
      //动态控制精度长度
      n = (r1 >= r2) ? r1 : r2;
      return ((arg2 * m - arg1 * m) / m).toFixed(n);
    } else if (type == 4) {
      let r1, r2, m;
      try {
        r1 = arg1.toString().split(".")[1].length
      } catch (e) {
        r1 = 0
      }
      try {
        r2 = arg2.toString().split(".")[1].length
      } catch (e) {
        r2 = 0
      }
      m = Math.pow(10, Math.max(r1, r2));
      return (arg1 * m + arg2 * m) / m;
    }
  }

另外一遍文章里面原文地址

/**
 * @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
 */

/**
 * 把错误的数据转正
 * strip(0.09999999999999998)=0.1
 */
function strip(num, precision = 12) {
  return +parseFloat(num.toPrecision(precision));
}

/**
 * Return digits length of a number
 * @param {*number} num Input number
 */
function digitLength(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;
}

/**
 * 把小数转成整数，支持科学计数法。如果是小数则放大成整数
 * @param {*number} num 输入数
 */
function float2Fixed(num) {
  if (num.toString().indexOf('e') === -1) {
    return Number(num.toString().replace('.', ''));
  }
  const dLen = digitLength(num);
  return dLen > 0 ? num * Math.pow(10, dLen) : num;
}

/**
 * 检测数字是否越界，如果越界给出提示
 * @param {*number} num 输入数
 */
function checkBoundary(num) {
  if (num > Number.MAX_SAFE_INTEGER || num < Number.MIN_SAFE_INTEGER) {
    console.warn(`${num} is beyond boundary when transfer to integer, the results may not be accurate`);
  }
}

/**
 * 精确乘法
 */
function times(num1, num2) {
  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);
}

/**
 * 精确加法
 */
function plus(num1, num2) {
  const baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
  return (times(num1, baseNum) + times(num2, baseNum)) / baseNum;
}

/**
 * 精确减法
 */
function minus(num1, num2) {
  const baseNum = Math.pow(10, Math.max(digitLength(num1), digitLength(num2)));
  return (times(num1, baseNum) - times(num2, baseNum)) / baseNum;
}

/**
 * 精确除法
 */
function divide(num1, num2) {
  const num1Changed = float2Fixed(num1);
  const num2Changed = float2Fixed(num2);
  checkBoundary(num1Changed);
  checkBoundary(num2Changed);
  return times((num1Changed / num2Changed), Math.pow(10, digitLength(num2) - digitLength(num1)));
}

/**
 * 四舍五入
 */
function round(num, ratio) {
  const base = Math.pow(10, ratio);
  return divide(Math.round(times(num, base)), base);
}

export { strip, plus, minus, times, divide, round, digitLength, float2Fixed };
export default { strip, plus, minus, times, divide, round, digitLength, float2Fixed };