Javascript中toFixed計(jì)算錯誤(依賴銀行家舍入法的缺陷)解決方法

console.log(.1+.2);
0.30000000000000004

var num = 0.045;
console.log(num.toFixed(2));
0.04

var num = 0.004;
console.log(num.toFixed(2));
0.00
var num = 0.014;
console.log(num.toFixed(2));
0.01
var num = 0.094;
console.log(num.toFixed(2));
0.09

var num = 0.006;
console.log(num.toFixed(2));
0.01
var num = 0.016;
console.log(num.toFixed(2));
0.02
var num = 0.096;
console.log(num.toFixed(2));
0.10

var num = 0.0051;
console.log(num.toFixed(2));
0.01
var num = 0.0052;
console.log(num.toFixed(2));
0.01
var num = 0.0059;
console.log(num.toFixed(2));
0.01

var num = 0.005;
console.log(num.toFixed(2));
var num = 0.015;
console.log(num.toFixed(2));
var num = 0.025;
console.log(num.toFixed(2));
var num = 0.035;
console.log(num.toFixed(2));
var num = 0.045;
console.log(num.toFixed(2));
var num = 0.055;
console.log(num.toFixed(2));
var num = 0.065;
console.log(num.toFixed(2));
var num = 0.075;
console.log(num.toFixed(2));
var num = 0.085;
console.log(num.toFixed(2));
var num = 0.095;
console.log(num.toFixed(2));

 Number.prototype.toFixed = function(length)
 {
 var carry = 0; //存放進(jìn)位標(biāo)志
 var num,multiple; //num為原浮點(diǎn)數(shù)放大multiple倍后的數(shù)，multiple為10的length次方
 var str = this + ''; //將調(diào)用該方法的數(shù)字轉(zhuǎn)為字符串
 var dot = str.indexOf("."); //找到小數(shù)點(diǎn)的位置
 if(str.substr(dot+length+1,1)>=5) carry=1; //找到要進(jìn)行舍入的數(shù)的位置，手動判斷是否大于等于5，滿足條件進(jìn)位標(biāo)志置為1
 multiple = Math.pow(10,length); //設(shè)置浮點(diǎn)數(shù)要擴(kuò)大的倍數(shù)
 num = Math.floor(this * multiple) + carry; //去掉舍入位后的所有數(shù)，然后加上我們的手動進(jìn)位數(shù)
 var result = num/multiple + ''; //將進(jìn)位后的整數(shù)再縮小為原浮點(diǎn)數(shù)
 /*
 * 處理進(jìn)位后無小數(shù)
 */
 dot = result.indexOf(".");
 if(dot < 0){
 result += '.';
 dot = result.indexOf(".");
 }
 /*
 * 處理多次進(jìn)位
 */
 var len = result.length - (dot+1);
 if(len < length){
 for(var i = 0; i < length - len; i++){
 result += 0;
 }
 }
 return result;
 }