//浮点数加法运算
function FloatAdd(arg1,arg2){
    var 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;
}

//浮点数减法运算
function FloatSub(arg1,arg2){
    var 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));
    //动态控制精度长度
    n=(r1>r2)?r1:r2;
    return ((arg1*m-arg2*m)/m).toFixed(n);
}

//浮点数乘法运算
function FloatMul(arg1,arg2)
{
    var m=0,s1=arg1.toString(),s2=arg2.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);
}

//浮点数除法运算
function FloatDiv(arg1,arg2){
    var t1=0,t2=0,r1,r2;
    try{t1=arg1.toString().split(".")[1].length}catch(e){}
    try{t2=arg2.toString().split(".")[1].length}catch(e){}
    with(Math){
        r1=Number(arg1.toString().replace(".",""));
        r2=Number(arg2.toString().replace(".",""));
        return (r1/r2)*pow(10,t2-t1);
    }
}

新闻名称：javascript浮点数加减乘除运算
文章来源：http://scyanting.com/article/ighcse.html