Flock Tech Screen - Completed

In a language of your choice, please write a program which accepts as input two arbitrarily nested arrays of strings, and returns the sum of the number of necessary one character substitutions multiplied by 2 to the power of the depth of nesting at which substitution must occur

For example:

yourFunction(
["I", ["love"], [[["awesome", "shiny"]]], "drones"],
["I", ["hate"], [[["magenta", "dirty"]]], "drains"]
)

should return 2(3) + 8(7 + 4) + 3 = 97

If the levels of nesting or the lengths of the strings do not match, return -1 so: yourFunction(["I", ["love"], [["awesome"]], "drones], ["I, ["hate"], [[["magenta"]]], "drains") should return -1

If the lengths of any fragment differ, return -1 so: yourFunction(["I", ["adore"], [[["red"]]], "drones], ["I, ["hate"], [[["magenta"]]], "drains") should return -1

Questions

1) What assumptions did you make?

Key assumptions was that I'd only ever be dealing with strings and arrays and that I'd only ever be dealing with two arguments.

2) What is the Big O of your solution? Please justify your answer.

O(KN^M) Where K is the is the max size of the strings (elements) in the array. N is the length of the array. M is the depth of nested arrays. Each nested level could have a bunch more nested lists, hence the exponent.

3) In what ways do you feel your code could be improved?

Aside from being better prepared to handle assumptions. I'm sure it can be refactored for readability and conciseness. I need to improve my commenting style. I'm sure that there's a faster way to do this, likely without recursion but I feel I've gotten a good balance of speed and readability.

4) What tests (if any) have you written? What tests do you feel you could still write?:

I wrote a small suite of tests to test for both sucessful and non-successful cases. I used Mocha and Chai to do so. The test I wrote made sure that:

If the levels of nesting or lengths of the strings did not match, it would return '-1';
If the lengths of the fragments differ, it would return '-1';
That otherwise, it would return the sum of the number of necessary one character substitutions multiplied by 2 to the power of the depth of nesting at which substitution must occur.

Ideally I'd like to have used an external library to randomly generate strings.

5) How do we run your code?:

Clone and download the repository to your local machine. Assuming you have both node and npm installed. Run npm install to install the dependencies. Then run npm test.