This script extracts all binary files from fb2 book and stores them in a dedicated folder

extractFilesFromFB2.js

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

const source = 'filename.fb2'
const targetFolder = 'result'

const xml = fs.readFileSync(source).toString()
if (!fs.existsSync('result')) fs.mkdirSync(targetFolder)

const pattern = /<binary[^>]*?id="([^"]*)"[^>]*?>(.*?)<\/binary>/gs

const matches = xml.matchAll(pattern)
for (const match of matches) {
  const [_, filename, content] = [...match]
  const filePath = path.join(targetFolder, filename)
  fs.writeFileSync(filePath, Buffer.from(content, 'base64'))
}