London | 26-ITP-May | Yonatan Teklemariam | Sprint 3 | strech-credit-card-validator

Sprint-3/4-stretch/Credit-Card-Validator.js

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+function validateCreditCard(cardNumber) {
+  if (cardNumber.length !== 16) {
+    return false; // this line of code checks whether the card number is 16 digits long or not
+  }
+  let index = 0;
+  while (index < cardNumber.length) {
+    if (cardNumber[index] < "0" || cardNumber[index] > "9") {
+      return false; // this line of code checks whether the card number is composed of digits not other characters
+    }
+    index++;
+  }
+  const firstDigit = cardNumber[0]; // first digit of the card number is stored for the purpose of checking up whether two digits are identical or not
+
+  index = 1;
+  while (index < cardNumber.length) {
+    if (cardNumber[index] !== firstDigit) {
+      break; // loop ends immediately here to give way to the next check
+    }
+    index++;
+  }
+  if (index === cardNumber.length) {
+    return false;
+  }
+  const lastDigit = cardNumber.slice(-1);
+  const lastNumber = Number(lastDigit);
+
+  if (lastNumber % 2 !== 0) {
+    return false; // this line of code checks whether the last digit of the card number is divisible by 2 in other words "even" or not
+  }
+
+  let total = 0;
+  index = 0;
+  while (index < cardNumber.length) {
+    total += Number(cardNumber[index]);
+    index++;
+  }
+  if (total <= 16) {
+    return false; // this line of code checks whether the sum of all the digits in the card number is more than 16 or not
+  }
+
+  return true;
+}
+console.log(validateCreditCard("9999777788880000"));