Simple solutions for isPalindrome, snake_case coverter and fibonacci

odin_js_exer

// check if word is palindrome
// can enter CAPS, nums, symbols etc..
function isPalindrome(string){
  return string.replace(/[^a-z]/gi, '').toLowerCase().split('').reverse().join('') === string.replace(/[^a-z]/gi, '').toLowerCase()
}

// n is index in the fibonacci sequence. 
// function returns n's number in the sequence. 
function fibo(n) {
  if (n < 0) return 'OOPS!'
  if (n <= 1) return n
  return fibo(n - 1) + fibo(n - 2)
}

// convert strings to snakeCase: hello_world
// I have found that it's easier done with Regular Expressions than with convert to an Array and 'algorithimize' it.
function makeSnake(string) {
  return string.replace(/[^a-z]/gi, ' ').replace(/ {1,}/g," ").trimRight().split(' ').join('_').toLowerCase()
}