Kata

Write a function that returns the sum of the passed arguments. The input arguments may be Numbers and/or String representations of numbers. The function must return a String.

Example

add(123, "321") === "444";
add("1234567890.0987654321", "8765432109.9012345678") === "9999999999.9999999999";
add("1.2.3", 1.23); === NaN;
add(0.1, 0.0001) === "0.1001";

Notes

The input numbers may be very very big and/or very very small. Addition must be exact - no floating point errors. The numbers are all positive and base 10. Some arguments may not be numbers. In these cases, return NaN. Remove trailing zeros and decimal point if possible.