hd-utils/lib/utils/array/groupBy.js

A handy utils for modern JS developers

/**
 * @description function to categorizes an array of objects by a key or condition. It also supports optional object transformation before grouping.
 * @example
 *
groupBy(
  [
  { name: 'Alice', age: 25 },
  { name: 'Bob', age: 30 },
  { name: 'Charlie', age: 25 },
  { name: 'David', age: 30 },
],
  'age',
  (person) => ({ ...person, isNew: person.age < 30 })
) //
{
  25: [
    { name: 'Alice', age: 25, isNew: true },
    { name: 'Charlie', age: 25, isNew: true },
  ],
  30: [
    { name: 'Bob', age: 30, isNew: false },
    { name: 'David', age: 30, isNew: false },
  ],
};

 */
export default function groupBy(array, keyOrCondition, transform) {
    const isFunction = typeof keyOrCondition === 'function';
    return array.reduce((result, item) => {
        const key = isFunction
            ? keyOrCondition(item)
            : item[keyOrCondition];
        if (!result[key]) {
            result[key] = [];
        }
        const transformedItem = transform ? transform(item, key) : item;
        result[key].push(transformedItem);
        return result;
    }, {});
}