Group by element in array by keyword

Question

I am developing an application on AngularJS (1) and I can not figure out how to split array of items in another array group by item.

I mean I have an array of different

Answer 1

You could use a hash table and collect the object in the arrays of the hash table.

var array = [{ name: "toto", uuid: 1111 }, { name: "tata", uuid: 2222 }, { name: "titi", uuid: 1111 }],
    hash = Object.create(null),
    result = [];

array.forEach(function (a) {
    if (!hash[a.uuid]) {
        hash[a.uuid] = [];
        result.push(hash[a.uuid]);
    }
    hash[a.uuid].push(a);
});

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

You can also use an established library like lodash to make it a lot simpler and save yourself the trouble:

let arr = [
    {"name": "toto", "uuid": 1111},
    {"name": "tata", "uuid": 2222},
    {"name": "titi", "uuid": 1111}
]

let grouped = _.groupBy(arr, 'uuid')

console.log(grouped)
console.log(Object.values(grouped))

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

Answer 3

You can use reduce and Object.values()

let a = [
    {"name": "toto", "uuid": 1111},
    {"name": "tata", "uuid": 2222},
    {"name": "titi", "uuid": 1111}
];

let b = Object.values(a.reduce((a,b) => {
    a[b.uuid] = a[b.uuid] ? a[b.uuid].concat(b) : [b];
    return a;
}, {}));

console.log(b);