JavaScript浮点数精度误差原理与修复方案

/*判断obj是否为一个整数*/
function isInteger(obj){
  return Math.floor(obj) === obj;
}
/**
* 将一个浮点数转换成整数，返回整数和倍数
* 如 3.14 》》314 倍数是100
*
*/
function toInteger(floatNum){
  var ret = {times:1,num:0};
  //是整数
  if(isInteger(floatNum)){
    ret.num = floatNum;
    return ret;
  }
  var strfi = floatNum + '';
  //查找小数点的下标
  var dotPos = strfi.indexOf('.');
  console.log('dotPos===='+dotPos);
  //获取小数的位数
  var len = strfi.substr(dotPos+1).length;
  console.log('len===='+len);
  //Math.pow(10,len)指定10的len次幂。
  var time = Math.pow(10,len);
  //将浮点数转化为整数
  var intNum = parseInt(floatNum*time + 0.5,10);
  console.log('intNum===='+intNum);
  ret.times = time;
  ret.num = intNum;
  return ret;
}
/**
*进行运算
*三个参数分别是要运算的两个数和运算符
*/
function operation(a,b,op){
  var o1 = toInteger(a);
  var o2 = toInteger(b);
  var n1 = o1.num;
  var n2 = o2.num;
  var t1 = o1.times;
  var t2 = o2.times;
  var max = t1 > t2 ? t1 : t2;
  var result = null;
  switch(op){
    case 'add':
      if(t1 === t2){
        result = n1 + n2;
      }else if(t1 > t2){
        result = n1 + n2 * (t1/t2);
      }else{
        result = n1 * (t2/t1) + n2;
      }
      return result / max;
      break;
    case 'subtract':
      if(t1 === t2){
        result = n1 - n2;
      }else if(t1 > t2){
        result = n1 - n2 * (t1/t2);
      }else{
        result = n1 * (t2/t1) - n2;
      }
      return result / max;
      break;
    case 'multiply':
      result = (n1 * n2)/(t1 * t2);
      return result;
      break;
    case 'divide':
      result = (n1 / n2)/(t2 / t1);
      return result;
      break;
  }
}