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38 lines
906 B
TypeScript
38 lines
906 B
TypeScript
// Loaded from https://deno.land/x/segno@v1.1.0/lib/validations/isISSN.ts
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// @ts-ignore allowing typedoc to build
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import { assertString } from '../helpers/assertString.ts';
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/**
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* @ignore
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*/
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const issn = '^\\d{4}-?\\d{3}[\\dX]$';
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type ISSNOptions = {
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requireHyphen?: boolean;
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caseSensitive?: boolean;
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};
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export const isISSN = (str: string, options: ISSNOptions = {}) => {
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assertString(str);
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let testIssn = issn;
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testIssn = options.requireHyphen ? testIssn.replace('?', '') : testIssn;
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const testIssnRegex = options.caseSensitive
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? new RegExp(testIssn)
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: new RegExp(testIssn, 'i');
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if (!testIssnRegex.test(str)) {
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return false;
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}
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const digits = str.replace('-', '').toUpperCase();
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let checksum = 0;
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for (let i = 0; i < digits.length; i++) {
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const 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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