Group by multiple values Underscore.JS but keep the keys and values

Question

I\'m trying to group the following array with objects:

[ { user_id: 301, alert_id: 199, deal_id: 32243 },
  { user_id: 301, alert_id: 200, deal_id: 32243 },
         


        

Answer 1

Use groupBy with a function that creates a composite key using user_id and alert_id. Then map across the groupings to get what you want:

    var list = [ { user_id: 301, alert_id: 199, deal_id: 32243 },
      { user_id: 301, alert_id: 200, deal_id: 32243 },
      { user_id: 301, alert_id: 200, deal_id: 107293 },
      { user_id: 301, alert_id: 200, deal_id: 277470 } ];

    var groups = _.groupBy(list, function(value){
        return value.user_id + '#' + value.alert_id;
    });

    var data = _.map(groups, function(group){
        return {
            user_id: group[0].user_id,
            alert_id: group[0].alert_id,
            deals: _.pluck(group, 'deal_id')
        }
    });

Answer 2

I would like to contribute a neat typescript ES6 group by.
I am not really sure how to tighten up the return value typing. Some trickery is needed there, but this works rather well for me.

/**
 * group the supplied list by a set of keys.
 * @param list the list of items to group.
 * @param children the key for the array of child items.
 * @param components the components to group by.
 */
groupByMultipleFields<T, K extends keyof T>(
    list: T[],
    children: string,
    ...components: K[]): any[] {

    var grouping = [...list.reduce((r, o) => {
        const key = components.map(_ => `${o[_]}`).join(" :: ");
        var keyed = r.get(key) || components.reduce((x, y) => { x[y] = o[y]; return x; }, <T>{});
        keyed[children] = keyed[children] || [];
        keyed[children].push(o);
        return r.set(key, keyed);
    }, new Map).values()];
    return grouping;

}

You will need to turn on the typescript compiler option "downlevelIteration": true to allow the new Map to iterate and return values().

Answer 3

For some specific task i had to to safe keys and values for it So i made this variant (with clean js):

/**
 * Group your items in array by multiple keys!
 *
 * @param collection
 * @param retrieveFunctions
 * @param compareFunctions
 * @returns {Array}
 */
function groupify(
    collection,
    retrieveFunctions = {attribute: value => value},
    compareFunctions = {attribute: (groupValue, value) => groupValue === value}
) {
    let groups = [];
    let keyValues = {};

    collection.forEach(item => {
        for (let attribute in retrieveFunctions) {
            keyValues[attribute] = retrieveFunctions.hasOwnProperty(attribute) ? retrieveFunctions[attribute](item[attribute]) : undefined;
        }
        let group = groups.find(group => {
            for (let key in retrieveFunctions) {
                if (!group && !group.keys[key]) {
                    return false;
                }
                if (compareFunctions[key] instanceof Function) {
                    if (!compareFunctions[key](group.keys[key], keyValues[key])) {
                        return false;
                    }
                } else if (group.keys[key] !== keyValues[key]) {
                    return false;
                }
            }

            return true;
        });

        !group ? groups.push({keys: keyValues, items: [item]}) : group.items.push(item);
        keyValues = {};
    });

    return groups;
}

Here the link on gist: groupify.js