fix

book/node_modules/lunr/build/wrapper_end

@@ -0,0 +1,29 @@
+
+  /**
+   * export the module via AMD, CommonJS or as a browser global
+   * Export code from https://github.com/umdjs/umd/blob/master/returnExports.js
+   */
+  ;(function (root, factory) {
+    if (typeof define === 'function' && define.amd) {
+      // AMD. Register as an anonymous module.
+      define(factory)
+    } else if (typeof exports === 'object') {
+      /**
+       * Node. Does not work with strict CommonJS, but
+       * only CommonJS-like enviroments that support module.exports,
+       * like Node.
+       */
+      module.exports = factory()
+    } else {
+      // Browser globals (root is window)
+      root.lunr = factory()
+    }
+  }(this, function () {
+    /**
+     * Just return a value to define the module export.
+     * This example returns an object, but the module
+     * can return a function as the exported value.
+     */
+    return lunr
+  }))
+})();