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

fetch-youtube-transcript.ts

import url from 'url';

interface Cue {
    transcriptCueRenderer: {
        cue: {
            simpleText: string;
        };
    };
}

interface CueGroup {
    transcriptCueGroupRenderer: {
        cues: Cue[];
    };
}

interface Response {
    actions: {
        updateEngagementPanelAction: {
            content: {
                transcriptRenderer: {
                    body: {
                        transcriptBodyRenderer: {
                            cueGroups: {
                                transcriptCueGroupRenderer: CueGroup;
                            },
                        },
                    },
                },
            },
        };
    }[];
}

async function getTranscriptJsonByVideoID(videoID: string): Promise<Response> {
    const response = await fetch(url.format({
        protocol: 'https',
        hostname: 'www.youtube.com',
        pathname: 'youtubei/v1/get_transcript',
        query: { key: 'AIzaSyAO_FJ2SlqU8Q4STEHLGCilw_Y9_11qcW8' },
    }), {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({
            context: { client: { clientName: 'WEB', clientVersion: '2.9999099' } },
            params: Buffer.from(`\n\x0b${videoID}`).toString('base64'),
        }),
    });

    return (await response.json()) as Response;
}

async function main() {
    const videoIDs = process.argv.slice(2);
    const promiseArray = videoIDs.map(getTranscriptJsonByVideoID);
    const settledPromises = await Promise.allSettled(promiseArray);

    for (const settled of settledPromises) {
        if (settled.status === 'fulfilled' && 'actions' in settled.value) {
            const { actions } = settled.value;
            const transcriptCues = actions
                .find(({ updateEngagementPanelAction }) => updateEngagementPanelAction)!
                .updateEngagementPanelAction.content.transcriptRenderer.body.transcriptBodyRenderer.cueGroups;

            const cueGroupsArray = Object.values(transcriptCues);
            const flattenedCues = cueGroupsArray.flatMap((cueGroup: CueGroup) => cueGroup.transcriptCueGroupRenderer.cues);
            console.log(
                flattenedCues.map((cue: Cue) => cue.transcriptCueRenderer.cue.simpleText).join('\n')
            );
        } else {
            if (settled.status === 'rejected') {
                console.error('rejected', settled.reason);
            } else if (!('actions' in settled.value)) {
                console.error('no actions');
            }
        }
    }
}

main();