extract bundle contents

map-source.js

const fs = require('fs');
const path = require('path');
const mkdirp = require('mkdirp');
const request = require('request-promise-native');
const { SourceMapConsumer } = require('source-map');

const usage = `
  usage:
    node map-source.js <bundle js url>
`

function extractSourceMappingURL(content) {
  const lines = content.split("\n");
  const last = lines.pop();
  const [, url] = /sourceMappingURL=(.+)$/.exec(last);
  return url;
}

function get(url) {
  return request({
    url,
    method: 'GET',
    gzip: true,
    headers: {
      'Accept': '*/*',
      'Accept-Encoding': 'gzip',
      'Accept-Language': 'en-US,en;q=0.9',
      'Cache-Control': 'no-cache',
      'Connection': 'keep-alive',
      'Pragma': 'no-cache',
      'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3221.0 Safari/537.36',
    }
  });
}

function replaceLastUrlPart(url, newLastPart) {
  const parts = url.split('/');
  parts.pop();
  return [...parts, newLastPart].join('/');
}

function targetFilePath(rootDir, mapSource) {
  const [, relPath] = /^.+:\/\/\/?(.+)$/.exec(mapSource);
  return path.join(rootDir, relPath.replace(/\?.+$/, ''));
}

async function main([bundleUrl]) {
  if (!bundleUrl) {
    console.log(usage);
    return process.exit(1);
  }

  const bundle = await get(bundleUrl);

  const sourceMappingRelativeURL = extractSourceMappingURL(bundle);
  if (!sourceMappingRelativeURL) {
    throw new Error('source mapping url not found!');
  }

  const sourceMappingURL = replaceLastUrlPart(bundleUrl, sourceMappingRelativeURL)

  const mapContent = await get(sourceMappingURL);
  const consumer = new SourceMapConsumer(JSON.parse(mapContent));

  const targetDir = bundleUrl.split('/').pop();
  const seen = {};
  consumer.eachMapping(mapping => {
    const { source } = mapping;
    if (!seen[source]) {
      seen[source] = 1;
      const content = consumer.sourceContentFor(source, true);
      if (content) {
        console.log('extracting', source);

        const target = targetFilePath(targetDir, source);

        mkdirp(path.dirname(target), err => {
          if (err) throw err;

          fs.writeFile(target, content, 'utf-8', err => {
            if (err) throw err;
          })
        });
      }
    }
  });
}

main(process.argv.slice(2));