jfpalchak / credit-card-validator

// A valid number: '4102080860435620'
// An invalid number: '4102080880435620'

Description: applyLuhn()

Test 1: "Check if input is a number, return number as an integer if so"
Code:
  const number = "1";
  applyLuhn(number)
Expected Output: 1 

Test 2: "Check if input is not a number, return NaN"
Code:   const number = "hello";
        applyLuhn(number);
Expected Output: NaN

Test 3: "Check if we have 16 numbers, return true"
Code:   const number = "4102080860435620";
        applyLuhn(number);
Expected Output: true

Test 4: "Create new array of integers and verify the length is 16 elements"
Code:   const number = "4102080860435620";
        applyLuhn(number);
Expected Output: [4,1,0,2,...]

Test 5: "Multiply index 1 in the array and every other index after index 1."
Code: array = [1234]
      for (i = 1; i < array.length; i = i + 2)
      array[i] = array[i] * 2;
Expected Result: [1438]

Test 6: "If element in new array is double digit, then we find the sum of both digits."
Code:
const number = "4102080860435620";
        applyLuhn(number);
Expected Results: [4,2,0,4,...]

Test 7: "If credit card number is valid, all numbers of the new array should sum together and return a value that ends with 0."
Code:
        const number = "4102080860435620";
        applyLuhn(number);
Expected Output: 50

Test 8: "If sum of modified credit card numbers ends with a 0, the card is valid, and function returns the card as Valid."
Code:
        const number = "4102080860435620";
        applyLuhn(number);
Expected Output: "This card number is valid."

Test 9: "If sum of modified credit card numbers doesn't end with a 0, the card is not valid, and function returns the card as Not Valid."
Code:
        const number = "4102080880435620";
        applyLuhn(number);
Expected Output: "This card number is Not Valid."