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chore: Strings: Credit Card Validation (#830)
* Add credit card number validator - Validates the credit card number based on Luhn algorithm * Test Cases: ValidateCreditCard * Auto-update DIRECTORY.md * Fix: Spell check * Add references and move const inside function * Add comments * Fix trailing spaces * Add short description * Remove trailing spaces Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
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@ -310,6 +310,7 @@
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* [ReverseString](https://github.com/TheAlgorithms/Javascript/blob/master/String/ReverseString.js)
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* [ReverseWords](https://github.com/TheAlgorithms/Javascript/blob/master/String/ReverseWords.js)
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* [ScrambleStrings](https://github.com/TheAlgorithms/Javascript/blob/master/String/ScrambleStrings.js)
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* [ValidateCreditCard](https://github.com/TheAlgorithms/Javascript/blob/master/String/ValidateCreditCard.js)
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* [ValidateEmail](https://github.com/TheAlgorithms/Javascript/blob/master/String/ValidateEmail.js)
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## Timing-Functions
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59
String/ValidateCreditCard.js
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59
String/ValidateCreditCard.js
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/**
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* Validate a given credit card number
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*
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* The core of the validation of credit card numbers is the Luhn algorithm.
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*
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* The validation sum should be completely divisible by 10 which is calculated as follows,
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* every first digit is added directly to the validation sum.
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* For every second digit in the credit card number, the digit is multiplied by 2.
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* If the product is greater than 10 the digits of the product are added.
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* This resultant digit is considered for the validation sum rather than the digit itself.
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*
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* Ref: https://www.geeksforgeeks.org/luhn-algorithm/
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*/
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const luhnValidation = (creditCardNumber) => {
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let validationSum = 0
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creditCardNumber.split('').forEach((digit, index) => {
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let currentDigit = parseInt(digit)
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if (index % 2 === 0) {
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// Multiply every 2nd digit from the left by 2
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currentDigit *= 2
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// if product is greater than 10 add the individual digits of the product to get a single digit
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if (currentDigit > 9) {
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currentDigit %= 10
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currentDigit += 1
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}
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}
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validationSum += currentDigit
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})
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return validationSum % 10 === 0
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}
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const validateCreditCard = (creditCardString) => {
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const validStartSubString = ['4', '5', '6', '37', '34', '35'] // Valid credit card numbers start with these numbers
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if (typeof creditCardString !== 'string') {
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throw new TypeError('The given value is not a string')
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}
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const errorMessage = `${creditCardString} is an invalid credit card number because `
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if (isNaN(creditCardString)) {
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throw new TypeError(errorMessage + 'it has nonnumerical characters.')
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}
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const creditCardStringLength = creditCardString.length
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if (!((creditCardStringLength >= 13) && (creditCardStringLength <= 16))) {
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throw new Error(errorMessage + 'of its length.')
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}
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if (!validStartSubString.some(subString => creditCardString.startsWith(subString))) {
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throw new Error(errorMessage + 'of its first two digits.')
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}
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if (!luhnValidation(creditCardString)) {
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throw new Error(errorMessage + 'it fails the Luhn check.')
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}
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return true
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}
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export { validateCreditCard }
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39
String/test/ValidateCreditCard.test.js
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39
String/test/ValidateCreditCard.test.js
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import { validateCreditCard } from '../ValidateCreditCard'
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describe('Validate credit card number', () => {
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it('should throw error if card number is boolean', () => {
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const invalidCC = true
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expect(() => validateCreditCard(invalidCC)).toThrow(
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'The given value is not a string'
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)
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})
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it('returns true if the credit card number is valid', () => {
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const validCreditCard = '4111111111111111'
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const validationResult = validateCreditCard(validCreditCard)
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expect(validationResult).toBe(true)
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})
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it('should throw an error on non-numeric character in given credit card number', () => {
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const nonNumericCCNumbers = ['123ABCDEF', 'ABCDKDKD', 'ADS232']
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nonNumericCCNumbers.forEach(nonNumericCC => expect(() => validateCreditCard(nonNumericCC)).toThrow(
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`${nonNumericCC} is an invalid credit card number because ` + 'it has nonnumerical characters.'
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))
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})
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it('should throw an error on credit card with invalid length', () => {
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const ccWithInvalidLength = ['41111', '4111111111111111111111']
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ccWithInvalidLength.forEach(invalidCC => expect(() => validateCreditCard(invalidCC)).toThrow(
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`${invalidCC} is an invalid credit card number because ` + 'of its length.'
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))
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})
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it('should throw an error on credit card with invalid start substring', () => {
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const ccWithInvalidStartSubstring = ['12345678912345', '23456789123456', '789123456789123', '891234567891234', '912345678912345', '31345678912345', '32345678912345', '33345678912345', '38345678912345']
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ccWithInvalidStartSubstring.forEach(invalidCC => expect(() => validateCreditCard(invalidCC)).toThrow(
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`${invalidCC} is an invalid credit card number because ` + 'of its first two digits.'
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))
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})
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it('should throw an error on credit card with luhn check fail', () => {
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const invalidCCs = ['411111111111111', '371211111111111', '49999999999999']
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invalidCCs.forEach(invalidCC => expect(() => validateCreditCard(invalidCC)).toThrow(
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`${invalidCC} is an invalid credit card number because ` + 'it fails the Luhn check.'
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))
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})
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})
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