add book.js

node_modules/lodash/internal/assignDefaults.js

@@ -0,0 +1,13 @@
+/**
+ * Used by `_.defaults` to customize its `_.assign` use.
+ *
+ * @private
+ * @param {*} objectValue The destination object property value.
+ * @param {*} sourceValue The source object property value.
+ * @returns {*} Returns the value to assign to the destination object.
+ */
+function assignDefaults(objectValue, sourceValue) {
+  return objectValue === undefined ? sourceValue : objectValue;
+}
+
+module.exports = assignDefaults;