groupby

groupArrayOfObjects.js

  function _group_by(list, key) {
      const groupBy = (array, key) => {
          // Return the end result
          return array.reduce((result, currentValue) => {
              // If an array already present for key, push it to the array. Else create an array and push the object
              (result[currentValue[key]] = result[currentValue[key]] || []).push(
                  currentValue
              );
              // Return the current iteration `result` value, this will be taken as next iteration `result` value and accumulate
              return result;
          }, []); // empty object is the initial value for result object
      };

      // Group by key as key to the list array
      return groupBy(list, key).filter(item => item);
  },

groupObject.js

function groupBy(data, key) {
    return data.reduce(function(storage, item) {
        const group = item[key];
        storage[group] = storage[group] || [];
        storage[group].push(item);
        return storage;
    }, {})
}