Complete 4-stretch/card-validator.js

Author: Temceo

Sprint-3/4-stretch/card-validator.js

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+/* 
+Here are the rules for a valid number:
+
+- Number must be 16 digits, all of them must be numbers.
+- You must have at least two different digits represented (all of the digits cannot be the same).
+- The final digit must be even.
+- The sum of all the digits must be greater than 16.
+
+For example, the following credit card numbers are valid:
+
+```markdown
+9999777788880000
+6666666666661666
+```
+
+And the following credit card numbers are invalid:
+
+```markdown
+a92332119c011112 (invalid characters)
+4444444444444444 (only one type of number)
+1111111111111110 (sum less than 16)
+6666666666666661 (odd final number)
+```
+
+These are the requirements your project needs to fulfill:
+
+- Make a JavaScript file with a name that describes its contents.
+- Create a function with a descriptive name which makes it clear what the function does. The function should take one argument, the credit card number to validate.
+- Write at least 2 comments that explain to others what a line of code is meant to do.
+- Return a boolean from the function to indicate whether the credit card number is valid.
+
+Good luck!
+*/
+
+const validateCard = (card) => {
+  const cardStr = String(card);
+  // Must have 16 digits
+  const has16Digits = cardStr.length === 16;
+  // Must be all digits
+  const isAllDigits = /^\d+$/.test(cardStr);
+  // Must have at least 2 numbers
+  const hasMoreThanOneDigit = cardStr.length > 1;
+  // Final digit must be even
+  const hasEvenFinalDigit = isAllDigits && (Number(cardStr) % 10) % 2 === 0;
+  // Sum of numbers must be at least 16
+  const sumOfNumbers = isAllDigits
+    ? cardStr.split("").reduce((acc, num) => acc + Number(num), 0)
+    : 0;
+
+  const hasSumOver15 = sumOfNumbers > 15;
+
+  // Must have more than one type of number
+  const hasMultipleDistinctDigits = new Set(cardStr.split("")).size > 1;
+
+  return has16Digits &&
+    hasMoreThanOneDigit &&
+    hasEvenFinalDigit &&
+    hasSumOver15 &&
+    hasMultipleDistinctDigits
+    ? "Valid card"
+    : "Invalid card";
+};
+
+console.log(validateCard(9999777788880000)); // valid
+console.log(validateCard(6666666666661666)); // valid
+console.log(validateCard("a92332119c011112")); // Invalid
+console.log(validateCard(4444444444444444)); // Invalid
+console.log(validateCard(1111111111111110)); // Invalid
+console.log(validateCard(6666666666666661)); // Invalid
+
+module.exports = validateCard;