1 files changed, 17 insertions, 0 deletions
diff --git a/packages/gitbook-core/src/createReducer.js b/packages/gitbook-core/src/createReducer.js
new file mode 100644
index 0000000..4af6373
--- /dev/null
+++ b/packages/gitbook-core/src/createReducer.js
@@ -0,0 +1,17 @@
+
+/**
+ * Helper to create a reducer that extend the store.
+ *
+ * @param  {String} property
+ * @param  {Function(state, action): state} reduce
+ * @return {Function(state, action): state}
+ */
+function createReducer(name, reduce) {
+    return function(state, action) {
+        const value = state[name];
+        state[name] = reduce(value, action);
+        return state;
+    };
+}
+
+module.exports = createReducer;