RecursiveCharacterTextSplitter

The recommended TextSplitter is the RecursiveCharacterTextSplitter. This will split documents recursively by different characters - starting with "\n\n", then "\n", then " ". This is nice because it will try to keep all the semantically relevant content in the same place for as long as possible.

Important parameters to know here are chunkSize and chunkOverlap. chunkSize controls the max size (in terms of number of characters) of the final documents. chunkOverlap specifies how much overlap there should be between chunks. This is often helpful to make sure that the text isn't split weirdly. In the example below we set these values to be small (for illustration purposes), but in practice they default to 4000 and 200 respectively.

import { RecursiveCharacterTextSplitter } from "langchain/text_splitter";

const text = `Hi.\n\nI'm Harrison.\n\nHow? Are? You?\nOkay then f f f f.
This is a weird text to write, but gotta test the splittingggg some how.\n\n
Bye!\n\n-H.`;
const splitter = new RecursiveCharacterTextSplitter({
  chunkSize: 10,
  chunkOverlap: 1,
});

const output = await splitter.createDocuments([text]);

You'll note that in the above example we are splitting a raw text string and getting back a list of documents. We can also split documents directly.

import { Document } from "langchain/document";
import { RecursiveCharacterTextSplitter } from "langchain/text_splitter";

const text = `Hi.\n\nI'm Harrison.\n\nHow? Are? You?\nOkay then f f f f.
This is a weird text to write, but gotta test the splittingggg some how.\n\n
Bye!\n\n-H.`;
const splitter = new RecursiveCharacterTextSplitter({
  chunkSize: 10,
  chunkOverlap: 1,
});

const docOutput = await splitter.splitDocuments([
  new Document({ pageContent: text }),
]);