@netlify/config/lib/utils/group.js

Netlify config module

// Group objects according to a key attribute.
// The key must exist in each object and be a string.
export const groupBy = function (objects, keyName) {
    const keys = [...new Set(objects.map((object) => object[keyName]))];
    return keys.map((key) => groupObjects(objects, keyName, key));
};
const groupObjects = function (objects, keyName, key) {
    return objects.filter((object) => object[keyName] === key);
};