js浮点数加减乘除

function mul(a,b){
    var c = 0,
          d = a.toString(),
          e = b.toString();
    try {
        c += d.split(".")[1].length;
    } catch (f) {}
    try {
        c += e.split(".")[1].length;
    } catch (f) {}
    return Number(d.replace(".", "")) * Number(e.replace(".", "")) / Math.pow(10, c);  
}

function add(a,b){
    var c, d, e;
    try {
        c = a.toString().split(".")[1].length;
    } catch (f) {
        c = 0;
    }
    try {
        d = b.toString().split(".")[1].length;
    } catch (f) {
        d = 0;
    }
    e = Math.pow(10, Math.max(c, d));
    return  (mul(a, e) + mul(b, e)) / e;
}

function sub(a, b) {
    var c, d, e;
    try {
        c = a.toString().split(".")[1].length;
    } catch (f) {
        c = 0;
    }
    try {
        d = b.toString().split(".")[1].length;
    } catch (f) {
        d = 0;
    }
    e = Math.pow(10, Math.max(c, d));
    return (mul(a, e) - mul(b, e)) / e;
}

function div(a, b) {
    var c, d, e = 0,
           f = 0;
    try {
        e = a.toString().split(".")[1].length;
    } catch (g) {
        e = 0;
    }
    try {
        f = b.toString().split(".")[1].length;
    } catch (g) {
        f = 0;
    }
    c = Number(a.toString().replace(".", ""));
    d = Number(b.toString().replace(".", ""));
    return mul(c / d, Math.pow(10, f - e));
}