isEven()

Write a function isEven() wich takes a single numeric argument and returns true if the number is even, and false otherwise

factorial()

Write a function factorial() wich takes a single numeric argument and returns the factorial of that number 4! = 4 x 3 x 2 x 1 0! = 1

kebabToSnake()

Write a function kebabToSnake() wich takes a single kebab-case string and returns the snake_cased version -->
kebabToSnake ("hello-world"); //"hello_world"
kebabToSnake ("hello"); //"hello"