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*   File System Store

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File System Store
=================

Compatibility

Only available on Node.js.

This example demonstrates how to setup chat history storage using the `LocalFileStore` KV store integration.

Usage[​](#usage "Direct link to Usage")
---------------------------------------

info

The path passed to the `.fromPath` must be a directory, not a file.

The `LocalFileStore` is a wrapper around the `fs` module for storing data as key-value pairs. Each key value pair has its own file nested inside the directory passed to the `.fromPath` method. The file name is the key and inside contains the value of the key.

    import fs from "fs";import { LocalFileStore } from "langchain/storage/file_system";import { AIMessage, HumanMessage } from "@langchain/core/messages";// Instantiate the store using the `fromPath` method.const store = await LocalFileStore.fromPath("./messages");// Define our encoder/decoder for converting between strings and Uint8Arraysconst encoder = new TextEncoder();const decoder = new TextDecoder();/** * Here you would define your LLM and chat chain, call * the LLM and eventually get a list of messages. * For this example, we'll assume we already have a list. */const messages = Array.from({ length: 5 }).map((_, index) => {  if (index % 2 === 0) {    return new AIMessage("ai stuff...");  }  return new HumanMessage("human stuff...");});// Set your messages in the store// The key will be prefixed with `message:id:` and end// with the index.await store.mset(  messages.map((message, index) => [    `message:id:${index}`,    encoder.encode(JSON.stringify(message)),  ]));// Now you can get your messages from the storeconst retrievedMessages = await store.mget(["message:id:0", "message:id:1"]);// Make sure to decode the valuesconsole.log(retrievedMessages.map((v) => decoder.decode(v)));/**[  '{"id":["langchain","AIMessage"],"kwargs":{"content":"ai stuff..."}}',  '{"id":["langchain","HumanMessage"],"kwargs":{"content":"human stuff..."}}'] */// Or, if you want to get back all the keys you can call// the `yieldKeys` method.// Optionally, you can pass a key prefix to only get back// keys which match that prefix.const yieldedKeys = [];for await (const key of store.yieldKeys("message:id:")) {  yieldedKeys.push(key);}// The keys are not encoded, so no decoding is necessaryconsole.log(yieldedKeys);/**[  'message:id:2',  'message:id:1',  'message:id:3',  'message:id:0',  'message:id:4'] */// Finally, let's delete the keys from the store// and delete the file.await store.mdelete(yieldedKeys);await fs.promises.rm("./messages", { recursive: true, force: true });

#### API Reference:

*   [LocalFileStore](https://v02.api.js.langchain.com/classes/langchain_storage_file_system.LocalFileStore.html) from `langchain/storage/file_system`
*   [AIMessage](https://v02.api.js.langchain.com/classes/langchain_core_messages.AIMessage.html) from `@langchain/core/messages`
*   [HumanMessage](https://v02.api.js.langchain.com/classes/langchain_core_messages.HumanMessage.html) from `@langchain/core/messages`

* * *

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