JavaScript native groupBy reduce

Question

I am using JavaScript native reduce, however I want to slightly change in the grouping to get my desired result. I have an array as follows:

const people = [
          


        

Answer 1

You could use a Map and a stringified object as key for grouping.

Later render the wanted array with objects of the keys and the grouped persons.

var people = [{ name: "John", age: 23, city: "Seattle", state: "WA" }, { name: "Mark", age: 25, city: "Houston", state: "TX" }, { name: "Luke", age: 26, city: "Seattle", state: "WA" }, { name: "Paul", age: 28, city: "Portland", state: "OR" }, { name: "Matt", age: 21, city: "Oakland", state: "CA" }, { name: "Sam", age: 24, city: "Oakland", state: "CA" }],
    arranged = Array.from(
        people.reduce((m, o) => {
            var key = JSON.stringify(Object.assign(...['city', 'state'].map(k => ({ [k]: o[k] }))));
            return m.set(key, (m.get(key) || []).concat({ name: o.name, age: o.age }));
        }, new Map),
        ([key, persons]) => Object.assign(JSON.parse(key), { persons })
    );

console.log(arranged);

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