Splitting by character

Character-based splitting is the simplest approach to text splitting. It divides text using a specified character sequence (default: "\n\n"), with chunk length measured by the number of characters.

Key points:

1. How text is split: by a given character separator.
2. How chunk size is measured: by character count.

You can choose between:

• .splitText — returns plain string chunks.
• .createDocuments — returns LangChain Document objects, useful when metadata needs to be preserved for downstream tasks.

npm

npm install @langchain/textsplitters

import { CharacterTextSplitter } from "@langchain/textsplitters";
import { readFileSync } from "fs";

// Example: read a long document
const stateOfTheUnion = readFileSync("state_of_the_union.txt", "utf8");

const splitter = new CharacterTextSplitter({
    separator: "\n\n",
    chunkSize: 1000,
    chunkOverlap: 200,
});
const texts = splitter.createDocuments([{ pageContent: stateOfTheUnion }]);
console.log(texts[0]);

Document {
    pageContent: 'Madam Speaker, Madam Vice President, our First Lady and Second Gentleman. Members of Congress and the Cabinet. Justices of the Supreme Court. My fellow Americans.  \n\nLast year COVID-19 kept us apart. This year we are finally together again. \n\nTonight, we meet as Democrats Republicans and Independents. But most importantly as Americans. \n\nWith a duty to one another to the American people to the Constitution. \n\nAnd with an unwavering resolve that freedom will always triumph over tyranny. \n\nSix days ago, Russia’s Vladimir Putin sought to shake the foundations of the free world thinking he could make it bend to his menacing ways. But he badly miscalculated. \n\nHe thought he could roll into Ukraine and the world would roll over. Instead he met a wall of strength he never imagined. \n\nHe met the Ukrainian people. \n\nFrom President Zelenskyy to every Ukrainian, their fearlessness, their courage, their determination, inspires the world.'
}

Use .createDocuments to propagate metadata associated with each document to the output chunks:

const metadatas = [{"document": 1}, {"document": 2}]
const documents = splitter.createDocuments(
    [{ pageContent: stateOfTheUnion }, { pageContent: stateOfTheUnion }],
    { metadatas: metadatas }
);
console.log(documents[0]);

Document {
    pageContent: 'Madam Speaker, Madam Vice President, our First Lady and Second Gentleman. Members of Congress and the Cabinet. Justices of the Supreme Court. My fellow Americans.  \n\nLast year COVID-19 kept us apart. This year we are finally together again. \n\nTonight, we meet as Democrats Republicans and Independents. But most importantly as Americans. \n\nWith a duty to one another to the American people to the Constitution. \n\nAnd with an unwavering resolve that freedom will always triumph over tyranny. \n\nSix days ago, Russia’s Vladimir Putin sought to shake the foundations of the free world thinking he could make it bend to his menacing ways. But he badly miscalculated. \n\nHe thought he could roll into Ukraine and the world would roll over. Instead he met a wall of strength he never imagined. \n\nHe met the Ukrainian people. \n\nFrom President Zelenskyy to every Ukrainian, their fearlessness, their courage, their determination, inspires the world.',
    metadata: {'document': 1}
}

Use .splitText to obtain the string content directly:

splitter.splitText(stateOfTheUnion)[0]

'Madam Speaker, Madam Vice President, our First Lady and Second Gentleman. Members of Congress and the Cabinet. Justices of the Supreme Court. My fellow Americans.  \n\nLast year COVID-19 kept us apart. This year we are finally together again. \n\nTonight, we meet as Democrats Republicans and Independents. But most importantly as Americans. \n\nWith a duty to one another to the American people to the Constitution. \n\nAnd with an unwavering resolve that freedom will always triumph over tyranny. \n\nSix days ago, Russia’s Vladimir Putin sought to shake the foundations of the free world thinking he could make it bend to his menacing ways. But he badly miscalculated. \n\nHe thought he could roll into Ukraine and the world would roll over. Instead he met a wall of strength he never imagined. \n\nHe met the Ukrainian people. \n\nFrom President Zelenskyy to every Ukrainian, their fearlessness, their courage, their determination, inspires the world.'

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