CODEWITHSUNDEEP
javascript
ivan milenkovic
ivan milenkovic

Reputation: 99

For loop iterating backwards?

I'm doing a credit card validation task and when I check given numbers who are 16-digit long everything seemed to work fine, but that was not the case when I entered 15-digit number. Then while debugging with console.logs I noticed that my 'i' values are not what I expect them to be and it seems that is the reason why it doesn't work properly, but I can't fix it. Here is my code, sorry for a lot of console.logs...

const validateCred = (array) => {
  let sum = 0;
  let newArray = array.slice()
  let popped = newArray.pop()
  console.log(array)
  console.log(newArray, popped)
  let reversedArray = newArray.reverse();
  console.log(reversedArray, popped)  
  for (let i = 0; i < reversedArray.length; i++) {
    if (i % 2 === 0) {
      console.log('value', i, array[i])
      array[i] = array[i] * 2 > 9 ? array[i] * 2 - 9 : array[i] * 2;
      console.log('new', array[i])
    } else {
      array[i] = array[i]
      console.log('value', i, array[i])
    }
    sum += array[i]
    console.log(sum)
  }
    sum += popped
    console.log(sum)
    sum % 10 === 0 ? console.log(true) : console.log(false)
}

const valid3 = [3, 7, 1, 6, 1, 2, 0, 1, 9, 9, 8, 5, 2, 3, 6];
validateCred(valid3)

So, after I reverse the array, I expected that 'i' of 0 would be 3 and 'i' of 1 to be 2, but as you can see from console.logs 'i' of 2 is 7 as if I didn't reverse the array. What am I doing wrong here?

Upvotes: 1

Views: 63

Answers (1)

Or Assayag
Or Assayag

Reputation: 6336

You declared for (let i = 0; i < reversedArray.length; i++) { but you are running on array[i]. You need to use reversedArray[i].

Upvotes: 2

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