1 | /* eslint-disable */
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2 | /*
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3 | * Luhn algorithm implementation in JavaScript
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4 | * Copyright (c) 2009 Nicholas C. Zakas
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5 | *
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6 | * Permission is hereby granted, free of charge, to any person obtaining a copy
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7 | * of this software and associated documentation files (the "Software"), to deal
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8 | * in the Software without restriction, including without limitation the rights
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9 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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10 | * copies of the Software, and to permit persons to whom the Software is
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11 | * furnished to do so, subject to the following conditions:
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12 | *
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13 | * The above copyright notice and this permission notice shall be included in
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14 | * all copies or substantial portions of the Software.
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15 | *
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16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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17 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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18 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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19 | * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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20 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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21 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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22 | * THE SOFTWARE.
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23 | */
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24 | ;
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25 |
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26 | function luhn10(identifier) {
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27 | var sum = 0;
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28 | var alt = false;
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29 | var i = identifier.length - 1;
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30 | var num;
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31 |
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32 | while (i >= 0) {
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33 | num = parseInt(identifier.charAt(i), 10);
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34 |
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35 | if (alt) {
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36 | num *= 2;
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37 | if (num > 9) {
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38 | num = (num % 10) + 1; // eslint-disable-line no-extra-parens
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39 | }
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40 | }
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41 |
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42 | alt = !alt;
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43 |
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44 | sum += num;
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45 |
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46 | i--;
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47 | }
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48 |
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49 | return sum % 10 === 0;
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50 | }
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51 |
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52 | module.exports = luhn10;
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