update readme for historydepthlimit

README.md

@@ -80,7 +80,7 @@ const useStoreWithUndo = create<StoreState>(
 ### Middleware Options
 
 ```tsx
-options: { omit: string[], allowUnchanged: boolean } = { omit: [], allowUnchanged: undefined }
+options: { omit?: string[], allowUnchanged?: boolean, historyDepthLimit?: number }
 ```
 
 #### **Omit fields from being tracked in history**
@@ -110,6 +110,19 @@ const useStore = create<StoreState>(
 );
 ```
 
+#### **Limit number of states stored**
+
+For performance reasons, you may want to limit the number of previous and future states stored in history. Setting `historyDepthLimit` will limit the number of previous and future states stored in the `zundo` store. By default, no limit is set.
+
+```tsx
+const useStore = create<StoreState>(
+  undoMiddleware(
+    set => ({ ... }),
+    { historyDepthLimit: 100 }
+  )
+);
+```
+
 ## API
 
 ### `undoMiddleware(config: StateCreator<TState>)`

src/factory.ts

@@ -60,14 +60,11 @@ const handleStoreUpdates = (
   const isUndo = action === 'undo';
   const currentActionStates = isUndo ? prevStates : futureStates;
   const otherActionStates = isUndo ? futureStates : prevStates;
-  const stateDepthLimit = isUndo
-    ? // default to historyLimit if no future limit.
-      options?.futureDepthLimit || options?.historyDepthLimit
-    : options?.historyDepthLimit;
+  const limit = options?.historyDepthLimit;
 
   if (currentActionStates.length > 0) {
     // check history limit
-    if (stateDepthLimit && otherActionStates.length >= stateDepthLimit) {
+    if (limit && otherActionStates.length >= limit) {
       // pop front
       otherActionStates.shift();
     }

src/middleware.ts

@@ -17,7 +17,6 @@ export interface Options {
   omit?: string[];
   allowUnchanged?: boolean;
   historyDepthLimit?: number;
-  futureDepthLimit?: number;
 }
 
 // custom zustand middleware to get previous state