js加減乘除進行精確計算

//加減乘除算法
Number.prototype.add = function (arg0, arg1) {
    var r1, r2, m;
    try {
        r1 = arg0.toString().split(".")[1].length
    } catch (e) {
        r1 = 0
    }
    try {
        r2 = arg1.toString().split(".")[1].length
    } catch (e) {
        r2 = 0
    }
    m = Math.pow(10, Math.max(r1, r2))
    return (arg0 * m + arg1 * m) / m
}
//減法
Number.prototype.sub = function (arg0, arg1) {
    return this.add(arg0, -arg1);
}
//乘法
Number.prototype.mul = function (arg0, arg1) {
    var m = 0, s1 = arg0.toString(), s2 = arg1.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 (arg0, arg1) {
    var t1 = 0, t2 = 0, r1, r2;
    try {
        t1 = arg0.toString().split(".")[1].length
    } catch (e) {
    }
    try {
        t2 = arg1.toString().split(".")[1].length
    } catch (e) {
    }
    with (Math) {
        r1 = Number(arg0.toString().replace(".", ""))
        r2 = Number(arg1.toString().replace(".", ""))
        return (r1 / r2) * pow(10, t2 - t1);
    }
}