import assertString from './util/assertString';
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var issn = '^\\d{4}-?\\d{3}[\\dX]$';
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export default function isISSN(str) {
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var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};
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assertString(str);
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var testIssn = issn;
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testIssn = options.require_hyphen ? testIssn.replace('?', '') : testIssn;
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testIssn = options.case_sensitive ? new RegExp(testIssn) : new RegExp(testIssn, 'i');
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if (!testIssn.test(str)) {
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return false;
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}
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var digits = str.replace('-', '').toUpperCase();
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var checksum = 0;
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for (var i = 0; i < digits.length; i++) {
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var digit = digits[i];
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checksum += (digit === 'X' ? 10 : +digit) * (8 - i);
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}
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return checksum % 11 === 0;
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}
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