Forgot to commit this...

CHANGELOG.md

@@ -5,7 +5,7 @@
 - Added support for greater or less than in `isFloat()`
   ([#544](https://github.com/chriso/validator.js/issues/544))
 - Added support for ISSN validation via `isISSN()`
-  ([#589](https://github.com/chriso/validator.js/pull/589))
+  ([#593](https://github.com/chriso/validator.js/pull/593))
 
 #### 6.0.0
 

lib/isISSN.js

@@ -0,0 +1,56 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = isISSN;
+
+var _assertString = require('./util/assertString');
+
+var _assertString2 = _interopRequireDefault(_assertString);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+var issn = /^\d{4}-\d{3}[\dX]$/;
+
+function isISSN(str) {
+  var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};
+
+  (0, _assertString2.default)(str);
+  var testIssn = options.case_sensitive ? issn : new RegExp(issn, 'i');
+  if (!testIssn.test(str)) {
+    return false;
+  }
+  var issnDigits = str.replace('-', '');
+  var position = 8;
+  var checksum = 0;
+  var _iteratorNormalCompletion = true;
+  var _didIteratorError = false;
+  var _iteratorError = undefined;
+
+  try {
+    for (var _iterator = issnDigits[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
+      var digit = _step.value;
+
+      var digitValue = digit.toUpperCase() === 'X' ? 10 : +digit;
+      checksum += digitValue * position;
+      --position;
+    }
+  } catch (err) {
+    _didIteratorError = true;
+    _iteratorError = err;
+  } finally {
+    try {
+      if (!_iteratorNormalCompletion && _iterator.return) {
+        _iterator.return();
+      }
+    } finally {
+      if (_didIteratorError) {
+        throw _iteratorError;
+      }
+    }
+  }
+
+  return checksum % 11 === 0;
+}
+module.exports = exports['default'];