30 lines
629 B
JavaScript
30 lines
629 B
JavaScript
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import assertString from './util/assertString';
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export default function isLuhnNumber(str) {
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assertString(str);
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var sanitized = str.replace(/[- ]+/g, '');
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var sum = 0;
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var digit;
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var tmpNum;
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var shouldDouble;
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for (var i = sanitized.length - 1; i >= 0; i--) {
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digit = sanitized.substring(i, i + 1);
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tmpNum = parseInt(digit, 10);
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if (shouldDouble) {
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tmpNum *= 2;
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if (tmpNum >= 10) {
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sum += tmpNum % 10 + 1;
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} else {
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sum += tmpNum;
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}
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} else {
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sum += tmpNum;
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}
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shouldDouble = !shouldDouble;
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}
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return !!(sum % 10 === 0 ? sanitized : false);
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}
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