ES6 Batch Util

es6_batch.js

// Async Chunking or Sync

class Batch {
  constructor(opt) {
    this.fn          = opt.fn;
    this.transformFn = opt.transformFn || null;
    this.args        = opt.args || [];
    this.argsIndex   = opt.argsIndex || 0;
    this.dataset     = opt.dataset || null;
    this.start       = 0;
    this.total       = opt.dataset ? opt.dataset.length : opt.total;
    this.chunk       = opt.chunk || 1;
    this.debug       = opt.debug || false;
  }

  async sendAsync() {
    const self = this;
    let batchData = [];

    async function handleBatch() {
      if (self.start >= self.total) {
        return batchData;
      }

      const promises = [];

      for (let i = self.start; i < self.start + self.chunk; i++) {
        if (i < self.total) {
          self.args[self.argsIndex] = self.dataset ? self.dataset[i] : i;

          const promise = self.fn.apply(null, self.args);

          promises.push(promise);
        }
      }

      const data = await Promise.all(promises);

      batchData = batchData.concat(self.transformFn ? self.transformFn(data) : data);

      if (self.debug) {
        console.log(batchData); // eslint-disable-line
      }

      self.start = self.start + self.chunk;

      return await handleBatch();
    }

    return handleBatch();
  }

  async sendSync() {
    const self = this;

    let batchData = [];

    async function handleBatch() {
      if (self.start >= self.total) {
        return batchData;
      }

      self.args[self.argsIndex] = self.dataset ? self.dataset[self.start] : self.start;

      const promise = self.fn.apply(null, self.args);

      const data = await promise;

      batchData = batchData.concat(self.transformFn ? self.transformFn(data) : data);

      if (self.debug) {
        console.log(batchData); // eslint-disable-line
      }

      self.start = self.start += 1;

      return await handleBatch();
    }

    return handleBatch();
  }
}


export default Batch;


// Example

// Promise
function p(i) {
  return new Promise(resolve => {
    setTimeout(() => {
      resolve({id: i});
    }, 300)
  })
}

// Even Number Transform Fn
function getEvenNumbers(data) {
  return _.chain(data)
  .filter(d => d.id % 2 === 0)
  .map(d => d.id)
  .value();
}

// Dataset to loop through
var data = {
  fulfillments: [],
};

for (var i = 0; i < 50; i++) {
  data.fulfillments.push({id: i});
}

var sync = new Batch({
  fn: p,
  transformFn: getEvenNumbers,
  args: [],
  start: 0,
  total: data.fulfillments.length,
  chunk: 5,
  debug: true
});

//sync.sendSync()
sync.sendAsync()
.then(data => {
  console.log('done', data);
})
.catch(err => {
  console.log('error', err);
});