bangbib/src/helpers.js

  export const group_by = (array, key) => {
    return array.reduce((result, currentValue) => {
      (result[currentValue[key]] = result[currentValue[key]] || []).push(
        currentValue
      );
      return result;
    }, {});
  };
  export const chunk = (arr, size) => arr.reduce((chunks, el, i) => (i % size
    ? chunks[chunks.length - 1].push(el)
    : chunks.push([el])) && chunks, []
  )