Run an async queue of records through an action and store/use result of each

sequenceWithResultStore.js

class TaskQueue {
  constructor(concurrency = 1) {
    this.concurrency = concurrency;
    this.running = 0;
    this.queue = [];
  }

  pushTask(task) {
    this.queue.push(task);
    this.next();
  }

  next() {
    while (this.running < this.concurrency && this.queue.length) {
      const task = this.queue.shift();
      // task(() => {
      task().then(() => {
        this.running -= 1;
        this.next();
      });
      this.running += 1;
    }
  }

  empty() {
    this.queue = [];
  }
}

// export default TaskQueue;

const sequenceWithResultStore = (records, action) => new Promise((resolve) => {
  const queue = new TaskQueue(); // Concurrency = 1
  let completed = 0;
  let lastResult = 0;
  const increment = () => {
    completed += 1;
    if (completed === records.length) { resolve(lastResult); }
  };

  records.forEach((record) => {
    const task = () => action(record, lastResult)
      .then((result) => {
        lastResult = result;
        console.log(lastResult);
        increment();
      })
      .catch((err) => {
        console.log('BATCH ERROR', err.message, record);
        increment();
      });
    queue.pushTask(task);
  });
});

const delay = ms => new Promise(res => setTimeout(res, ms));

const testAction = (current, lastResult = 0) =>
  new Promise(async (resolve) => {
    await delay(500);
    resolve(current + lastResult);
  });

const testBatch = async () => {
  const result = await sequenceWithResultStore([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], testAction);
  console.log(`Result: ${result}`);
};

testBatch();