mongo works

parts/3/followAlong/node_modules/mongoose/lib/helpers/omitUndefined.js

@@ -0,0 +1,20 @@
+'use strict';
+
+module.exports = function omitUndefined(val) {
+  if (val == null || typeof val !== 'object') {
+    return val;
+  }
+  if (Array.isArray(val)) {
+    for (let i = val.length - 1; i >= 0; --i) {
+      if (val[i] === undefined) {
+        val.splice(i, 1);
+      }
+    }
+  }
+  for (const key of Object.keys(val)) {
+    if (val[key] === void 0) {
+      delete val[key];
+    }
+  }
+  return val;
+};