Batch splitter

split_batches..js

const sizeLimit = 1000000;
const lengthLimit = 500;

const getSize = obj => Buffer.byteLength( JSON.stringify( obj ) );
const isUnderLimits = batch => batch.length <= lengthLimit && getSize( batch ) <= sizeLimit;

module.exports = records => records.reduce( ( batches, record ) => {
  if ( isUnderLimits( [].concat( batches[0], record ) ) ) {
    batches[0].push( record );
  } else {
    batches.unshift( [ record ] );
  }
  return batches;
}, [] );