office-text-extractor/build/lib.js

Yet another library to extract text from MS Office and PDF files

// source/lib.ts
// The source code for the library.
import encoding from 'text-encoding';
import { fileTypeFromBuffer as getFileType } from 'file-type';
import { readFile, fetchUrl } from './util.js';
/**
 * The text extractor class.
 */
export class TextExtractor {
    // The list of methods supported by this instance of the extractor.
    methods = [];
    // An encoder-decoder pair for buffers and strings.
    encoder = new encoding.TextEncoder();
    decoder = new encoding.TextDecoder();
    /**
     * Registers a new method to this instance of the extractor.
     *
     * @param method The method of text extraction to add.
     * @returns The current instance, for method chaining.
     */
    addMethod = (method) => {
        this.methods.push(method);
        return this;
    };
    /**
     * Extracts text from the given input.
     *
     * @param payload The input and type of input to extract text from.
     * @returns The extracted text as a simple string.
     */
    extractText = async ({ input, type }) => {
        // Turn the input into a buffer containing the file's contents.
        let preparedInput;
        if (typeof input === 'string') {
            if (type === 'file')
                preparedInput = await readFile(input);
            else if (type === 'url')
                preparedInput = await fetchUrl(input);
            else
                preparedInput = this.encoder.encode(input);
        }
        else {
            preparedInput = input;
        }
        // Check the mime type of the file. If there is no mime type, it's most
        // likely a text or CSV file. 
        const mimeDetails = await getFileType(preparedInput);
        if (!mimeDetails)
            return this.decoder.decode(preparedInput);
        // Find the extractor that can handle that mime type, and call it.
        const extractor = this.methods.findLast((method) => method.mimes.includes(mimeDetails.mime));
        if (!extractor?.apply) {
            const message = `text-extractor: could not find a method to handle ${mimeDetails.mime}`;
            throw new Error(message);
        }
        return extractor.apply(preparedInput);
    };
}