add book.js

node_modules/lodash/internal/arraySum.js

@@ -0,0 +1,20 @@
+/**
+ * A specialized version of `_.sum` for arrays without support for callback
+ * shorthands and `this` binding..
+ *
+ * @private
+ * @param {Array} array The array to iterate over.
+ * @param {Function} iteratee The function invoked per iteration.
+ * @returns {number} Returns the sum.
+ */
+function arraySum(array, iteratee) {
+  var length = array.length,
+      result = 0;
+
+  while (length--) {
+    result += +iteratee(array[length]) || 0;
+  }
+  return result;
+}
+
+module.exports = arraySum;