JS浮点类型运算精度丢失问题解决办法

//加法  

Number.prototype.add = function(arg){  

    var r1,r2,m;  

    try{r1=this.toString().split(".")[1].length}catch(e){r1=0}  

    try{r2=arg.toString().split(".")[1].length}catch(e){r2=0}  

    m=Math.pow(10,Math.max(r1,r2))  

    return (this*m+arg*m)/m  

}  

 

//减法  

Number.prototype.sub = function (arg){  

    return this.add(-arg);  

}  

 

//乘法  

Number.prototype.mul = function (arg)  

{  

    var m=0,s1=this.toString(),s2=arg.toString();  

    try{m+=s1.split(".")[1].length}catch(e){}  

    try{m+=s2.split(".")[1].length}catch(e){}  

    return Number(s1.replace(".",""))*Number(s2.replace(".",""))/Math.pow(10,m)  

}  

 

//除法  

Number.prototype.div = function (arg){  

    var t1=0,t2=0,r1,r2;  

    try{t1=this.toString().split(".")[1].length}catch(e){}  

    try{t2=arg.toString().split(".")[1].length}catch(e){}  

    with(Math){  

        r1=Number(this.toString().replace(".",""))  

        r2=Number(arg.toString().replace(".",""))  

        return (r1/r2)*pow(10,t2-t1);  

    }  

}

 

应用：

    alert(0.1+0.2)                       //  0.30000000000000004 

    alert(Number(0.1).add(0.2));         //  0.3