TypeScript code to fetch one or more YouTube transcripts as plain text without API key

fetch-youtube-transcript.ts

import url from 'url';

import parse from 'html-dom-parser';
import { Element, Text } from 'domhandler';
import { decodeXML } from 'entities';

async function getHtmlByVideoID(videoID: string): Promise<string> {
    const reponse = await fetch(url.format({
        protocol: 'https',
        hostname: 'www.youtube.com',
        pathname: 'watch',
        query: { v: videoID },
    }));

    return (await reponse.text());
}

async function main() {
    const videoIDsFromCommandline = process.argv.slice(2);
    let videoIDs = videoIDsFromCommandline;
    let videoIDsToRetry: string[] = [];

    while (videoIDs.length > 0) {
        const promiseArray = videoIDs.map(getHtmlByVideoID);
        const settledPromises = await Promise.allSettled(promiseArray);

        for (const [settledNum, settled] of settledPromises.entries()) {
            const videoID = `${videoIDs[settledNum]}`;

            if (settled.status === 'fulfilled') {
                if (settled.value) {
                    const dom = parse(settled.value);

                    const data = ((((dom[1] as Element).children[1] as Element).children[0] as Element).children[0] as Text).data;
                    const startsWith = 'var ytInitialPlayerResponse = ';

                    if (data.includes(startsWith) && data.endsWith(';')) {
                        const json = JSON.parse(data.substring(startsWith.length, data.length - 1));
                        if (!('captions' in json)) {
                            console.error('no captions', videoID);
                        } else {
                            const xml = await (await fetch(json.captions.playerCaptionsTracklistRenderer.captionTracks[0].baseUrl)).text();
                            const dom = parse(xml);
                            for (const dn of (dom[1] as Element).children)
                                console.log(decodeXML(((dn as Element).children[0] as Text).data));
                        }
                    }
                }
            } else if (settled.status === 'rejected') {
                console.error(`rejected ${videoID}`, settled.reason);
                videoIDsToRetry.push(videoID);
            }
        }

        videoIDs = videoIDsToRetry;
        videoIDsToRetry = [];
    }
}

main();