JavaScript解決浮點數計算不準確問題的方法分析

/*判斷obj是否為一個整數*/
function isInteger(obj){
 return Math.floor(obj) === obj;
}
/**
* 將一個浮點數轉換成整數，返回整數和倍數
* 如 3.14 》》314 倍數是100
*
*/
function toInteger(floatNum){
 var ret = {times:1,num:0};
 //是整數
 if(isInteger(floatNum)){
 ret.num = floatNum;
 return ret;
 }
 var strfi = floatNum + '';
 //查找小數點的下標
 var dotPos = strfi.indexOf('.');
 console.log('dotPos===='+dotPos);
 //獲取小數的位數
 var len = strfi.substr(dotPos+1).length;
 console.log('len===='+len);
 //Math.pow(10,len)指定10的len次冪。
 var time = Math.pow(10,len);
 //將浮點數轉化為整數
 var intNum = parseInt(floatNum*time + 0.5,10);
 console.log('intNum===='+intNum);
 ret.times = time;
 ret.num = intNum;
 return ret;
}
/**
*進行運算
*三個參數分別是要運算的兩個數和運算符
*/
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;
 }
}