songguoqiang / happy-birthday-seth

Happy birthday, Seth!!!

Task: Solve the following Caesar cipher challenge to get to your birthday surprise.

Your birthday surprise is at: "Hgx Angwkxw Hkvatkw Khtw, Vhgvhkwx Ahmxe & Lahiibgz Ftee, #sxkhmph-yhkmrmakxx". Pass all the tests to find out where that is!

Instructions

1. Clone this repository
2. Install dependencies: npm install
3. Run mocha test.js --watch (to terminate the tests, hit Ctrl C)
4. To activate the next test, change xit(...) to it(...) in test.js (x is mocha's way of skipping tests')
5. Implement your solution in solution.js
6. When all tests have passed, run node solution.js "Hgx Angwkxw Hkvatkw Khtw, Vhgvhkwx Ahmxe & Lahiibgz Ftee, #sxkhmph-yhkmrmakxx"
7. Get to your birthday surprise!

What is a Caesar cipher?

Given 2 arguments (string and shiftAmount), encrypt(string, shiftAmount) will convert a given string into a Caesar cipher by shifting each letter in the string "up" by the amount as indicated by shiftAmount.

Similarly, decrypt(string, shiftAmount) will decrypt a caesar cipher into a string by shifting each letter in the encrypted string "down" by the amount indicated by shiftAmount

Both encrypt(string, shiftAmount) and decrypt(string, shiftAmount) applies only to upper-case and lower-case alphabets (i.e. it does not shift non-alphabetical characters such as -, _, #, <space>, !!, etc). The second argument to the decrypt(string, shiftAmount) and encrypt(string, shiftAmount) (i.e. shiftAmount) will be a positive number greater than 0.

Examples:

• encrypt('abc', 1) would move each letter "up" by 1 charCode and return bcd.
• encrypt('abc', 2) would move each letter "up" by 2 charCodes and return cde.
• decrypt('cde', 2) would move each letter "down" by 2 charCodes and return abc.
• encrypt("it's my birthday", 1) would move each letter up by 1 charCode and return ju't nz cjsuiebz
• decrypt("ju't nz cjsuiebz", 1) would return it's my birthday

Hint:

• The difference between decrypt() and encrypt() is just the changing of 1 mathematical operation at 2 places
• Caesar Cipher : http://en.wikipedia.org/wiki/Caesar_cipher
• Char codes: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/String/fromCharCode
• More char codes: https://www.w3schools.com/charsets/ref_html_ascii.asp