/*js浮點(diǎn)數(shù)運(yùn)算問題解決辦法
   @params type: 1乘法奈懒，2除法 3減法，4加法
   @params arg1 arg2 按照表達(dá)式順序來
   */

  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
      //動(dòng)態(tài)控制精度長度
      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 解決浮動(dòng)運(yùn)算問題宪巨，避免小數(shù)點(diǎn)后產(chǎn)生多位數(shù)和計(jì)算精度損失磷杏。
 * 問題示例：2.3 + 2.4 = 4.699999999999999，1.0 - 0.9 = 0.09999999999999998
 */

/**
 * 把錯(cuò)誤的數(shù)據(jù)轉(zhuǎn)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;
}

/**
 * 把小數(shù)轉(zhuǎn)成整數(shù)捏卓，支持科學(xué)計(jì)數(shù)法极祸。如果是小數(shù)則放大成整數(shù)
 * @param {*number} num 輸入數(shù)
 */
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;
}

/**
 * 檢測(cè)數(shù)字是否越界，如果越界給出提示
 * @param {*number} num 輸入數(shù)
 */
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`);
  }
}

/**
 * 精確乘法
 */
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);
}

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

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

/**
 * 精確除法
 */
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 };