JWT Autorization / Logging in and registering

node_modules/validator/es/lib/isISSN.js

@@ -0,0 +1,23 @@
+import assertString from './util/assertString';
+var issn = '^\\d{4}-?\\d{3}[\\dX]$';
+export default function isISSN(str) {
+  var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};
+  assertString(str);
+  var testIssn = issn;
+  testIssn = options.require_hyphen ? testIssn.replace('?', '') : testIssn;
+  testIssn = options.case_sensitive ? new RegExp(testIssn) : new RegExp(testIssn, 'i');
+
+  if (!testIssn.test(str)) {
+    return false;
+  }
+
+  var digits = str.replace('-', '').toUpperCase();
+  var checksum = 0;
+
+  for (var i = 0; i < digits.length; i++) {
+    var digit = digits[i];
+    checksum += (digit === 'X' ? 10 : +digit) * (8 - i);
+  }
+
+  return checksum % 11 === 0;
+}