CODE EXAMPLE FOR JAVASCRIPT

how to group an array of objects

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
};