Purify

• Working in pairs
• Fork and clone repo
• Run npm install to install jest
• Create a test folder where your tests will live
• Implement tests for each function. Provide at least 2 test cases for each function
• Rewrite functions to become pure functions. Use tests to verify the inputs to each function remain unchanged by the execution of each function
• Replace instance of var with constor let as appropriate
• Replace for loops etc with relevant array methods
• Submit pull request with completed code