Someone give me some coding test on CoderByte. Here are the questions and my answers.

ApproachingFibonacci.js

/*
  Have the function 
  ArithGeo(arr)
  take the array of numbers stored in 
  arr
  and return the string 
  "Arithmetic"
  if the sequence follows an arithmetic pattern or return 
  "Geometric"
  if it follows a geometric pattern. If the sequence doesn't follow either pattern return 
  -1
  . An arithmetic sequence is one where the difference between each of the numbers is consistent, 
  where as in a geometric sequence, each term after the first is multiplied by some constant or common ratio. 
  Arithmetic example: [2, 4, 6, 8] and 
  Geometric example: [2, 6, 18, 54]. 
  Negative numbers may be entered as parameters, 
  0 will not be entered, and no array will contain all the same elements. 
*/

function isArithmetic(arr) {
  let output = true
  
  const delta = arr[0] - arr[1]

  for (let i = 0; i < arr.length -1; i++) {
    if (delta !== arr[i] - arr[i + 1]) {
      output = false
      break
    }
  }

  return output
}

function isGeometric(arr) {
  let output = true

  const delta = arr[1] / arr[0]

  for (let i = 0; i < arr.length -1; i++) {
    if (delta !== arr[i + 1] / arr[i]) {
      output = false
      break
    }
  }

  return output
}

function ArithGeo(arr) {
  
  // 0 will not be entered as param.
  if (arr.includes(0)) {
    throw new Error('0 is not allowed')
  }

  // No array will contain all the same elements.
  arr = Array.from(new Set(arr));

  if (isArithmetic(arr)) return 'Arithmetic'
  if (isGeometric(arr)) return 'Geometric'
  return undefined
}

console.log(ArithGeo([2, 4, 6, 8])) // Arithmetic
console.log(ArithGeo([2, 6, 18, 54])) // Geometric
console.log(ArithGeo([2, 4, 6, 10])) // undefined
console.log(ArithGeo([0, 1, 2])) // Error

ArithGeo.js

/*
  Have the function 
   ArithGeo(arr)
   take the array of numbers stored in 
  arr
  and return the string 
  "Arithmetic"
   if the sequence follows an arithmetic pattern or return 
  "Geometric"
   if it follows a geometric pattern. If the sequence doesn't follow either pattern return 
  -1
  . An arithmetic sequence is one where the difference between each of the numbers is consistent, 
  where as in a geometric sequence, each term after the first is multiplied by some constant or common ratio. 
  Arithmetic example: [2, 4, 6, 8] and 
  Geometric example: [2, 6, 18, 54]. 
  Negative numbers may be entered as parameters, 
  0 will not be entered, and no array will contain all the same elements. 
*/

function isArithmetic(arr) {
  let output = true
  
  const delta = arr[0] - arr[1]

  for (let i = 0; i < arr.length -1; i++) {
    if (delta !== arr[i] - arr[i + 1]) {
      output = false
      break
    }
  }

  return output
}

function isGeometric(arr) {
  let output = true

  const delta = arr[1] / arr[0]

  for (let i = 0; i < arr.length -1; i++) {
    if (delta !== arr[i + 1] / arr[i]) {
      output = false
      break
    }
  }

  return output
}

function ArithGeo(arr) {
  
  // 0 will not be entered as param.
  if (arr.includes(0)) {
    throw new Error('0 is not allowed')
  }

  // No array will contain all the same elements.
  arr = Array.from(new Set(arr));

  if (isArithmetic(arr)) return 'Arithmetic'
  if (isGeometric(arr)) return 'Geometric'
  return undefined
}

console.log(ArithGeo([2, 4, 6, 8])) // Arithmetic
console.log(ArithGeo([2, 6, 18, 54])) // Geometric
console.log(ArithGeo([2, 4, 6, 10])) // undefined
console.log(ArithGeo([0, 1, 2])) // Error

DashInsertII.js

/*
  Have the function 
   DashInsertII(str)
  insert dashes ('-') between each two odd numbers and insert asterisks ('*') between each two even numbers in 
  str
  . For example: if 
  str
   is 
  4546793
   the output should be 
  454*67-9-3
  . Don't count zero as an odd or even number.
*/

const isEven = n => n % 2 === 0
const isOdd = n => !isEven(n)

function DashInsertII(str) {
  str = (str + '').split('')

  let result = ''

  for (let i = 0; i < str.length; i++) {
    result += str[i]

    if (str[i] === '0' && str[i + 1] === '0') continue
    if (isEven(str[i]) && isEven(str[i + 1])) result += '*'
    if (isOdd(str[i]) && isOdd(str[i + 1])) result += '-'
  }
  
  // Clean-up trailing - or *
  result = result.replace(/[-|*]$/, '')
  
  return result
}

console.log(DashInsertII('4546793')) // Output: 454*67-9-3
console.log(DashInsertII('45467930022')) // Output: 454*67-9-300*2*2