extract-text-from-vtt.js

const fs = require('node:fs')
const path = require('node:path')

const BUFFER_ENCODING = 'utf8'

const getFilePath = (filename) => path.resolve(__dirname, filename)

const format = (filename) => {
  return fs
    .readFileSync(getFilePath(filename), BUFFER_ENCODING)
    .replace(/\r/g, '')
    .trim()
    .replace(/(\d+\n)?\d{2}:\d{2}:\d{2}\.\d{3} --> \d{2}:\d{2}:\d{2}\.\d{3}\n/g, '')
    .replace(/^\s*[\r\n]/gm, '')
}

const writeFile = (filename, content) => fs.writeFileSync(getFilePath(filename), content, BUFFER_ENCODING)

const outputContent = format('input.vtt')
writeFile('output.vtt', outputContent)