add book.js

node_modules/lodash/lang/isNull.js

@@ -0,0 +1,21 @@
+/**
+ * Checks if `value` is `null`.
+ *
+ * @static
+ * @memberOf _
+ * @category Lang
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is `null`, else `false`.
+ * @example
+ *
+ * _.isNull(null);
+ * // => true
+ *
+ * _.isNull(void 0);
+ * // => false
+ */
+function isNull(value) {
+  return value === null;
+}
+
+module.exports = isNull;