js解决浮点数的加减乘除

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