关于JS小数计算误差的解决办法

//加法

Number.prototype.add = function (arg) {

    var r1 = 0, r2 = 0, m;

    //获取小数的位数并取最大值

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

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

    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();

    //小数位数相加

    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) { }

    //将小数点去掉转换为整数

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

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

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

}