const urls = ['url1', 'url2', 'url3'];

​

function fakeFetch(url, params = '-') {

  // этот вывод в консоль покажет порядок вызовов с их входящими параметрами

  console.log(`fakeFetch to: ${url} with params: ${params}`);

  return new Promise(resolve => {

    setTimeout(() => resolve(`${url} is DONE`), 1000);

  })

};

​

function generatorWay(callback) {

  function* generateSequence() {

    let results;

    // noprotect

    for (let url of urls) {

      results = yield fakeFetch(url, results);

    }

    return results;

  }

​

  function execute(generator, yieldValue) {

    let next = generator.next(yieldValue);

    if (!next.done) {

      return next.value

        .then(result => execute(generator, result));

    }

    callback(next.value);

  }

  execute(generateSequence())

}

​

generatorWay(result => console.log(`result: ${result}`))

​