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// Run from the dev tools console of any Youtube video
// Accurate as of June 23, 2017.

// ES6 version
const videoUrls = ytplayer.config.args.adaptive_fmts
  .split(',')
  .map(item => item
    .split('&')
    .reduce((prev, curr) => (curr = curr.split('='),
      Object.assign(prev, {[curr[0]]: decodeURIComponent(curr[1])})
    ), {})
  )
  .reduce((prev, curr) => Object.assign(prev, {
    [curr.quality_label || curr.type]: curr
  }), {});

console.log(videoUrls);

// ES5 version
var videoUrls = ytplayer.config.args.adaptive_fmts
  .split(',')
  .map(function (item) {
    return item
      .split('&')
      .reduce(function (prev, curr) {
        curr = curr.split('=');
        return Object.assign(prev, {[curr[0]]: decodeURIComponent(curr[1])})
      }, {});
  })
  .reduce(function (prev, curr) {
    return Object.assign(prev, {
      [curr.quality_label || curr.type]: curr
    });
  }, {});

console.log(videoUrls);