card-validator/src/luhn-10.js

A library for validating credit card fields

/* eslint-disable */
/*
 * Luhn algorithm implementation in JavaScript
 * Copyright (c) 2009 Nicholas C. Zakas
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
"use strict";

function luhn10(identifier) {
  var sum = 0;
  var alt = false;
  var i = identifier.length - 1;
  var num;

  while (i >= 0) {
    num = parseInt(identifier.charAt(i), 10);

    if (alt) {
      num *= 2;
      if (num > 9) {
        num = (num % 10) + 1; // eslint-disable-line no-extra-parens
      }
    }

    alt = !alt;

    sum += num;

    i--;
  }

  return sum % 10 === 0;
}

module.exports = luhn10;