some progress

node_modules/mongoose/lib/cast/boolean.js

@@ -0,0 +1,32 @@
+'use strict';
+
+const CastError = require('../error/cast');
+
+/**
+ * Given a value, cast it to a boolean, or throw a `CastError` if the value
+ * cannot be casted. `null` and `undefined` are considered valid.
+ *
+ * @param {Any} value
+ * @param {String} [path] optional the path to set on the CastError
+ * @return {Boolean|null|undefined}
+ * @throws {CastError} if `value` is not one of the allowed values
+ * @api private
+ */
+
+module.exports = function castBoolean(value, path) {
+  if (module.exports.convertToTrue.has(value)) {
+    return true;
+  }
+  if (module.exports.convertToFalse.has(value)) {
+    return false;
+  }
+
+  if (value == null) {
+    return value;
+  }
+
+  throw new CastError('boolean', value, path);
+};
+
+module.exports.convertToTrue = new Set([true, 'true', 1, '1', 'yes']);
+module.exports.convertToFalse = new Set([false, 'false', 0, '0', 'no']);