How to get unique objects from array of objects by all properties?

Question

Given this typescript code using lodash:

import * as _ from "lodash/fp";

const range = _.range(0, 1000);
let objects = _.uniq(range.map((i) => {
    let foo = "foo";
    let bar = "bar";

    if (i < 5) {
        foo += i.toString(10);
    }

    if (i > 995) {
        bar += i.toString(10);
    }

    return {
        foo,
        bar,
    };
}));

I was expecting to only see the object

{
    "foo": "foo",
    "bar": "bar"
}

once and the total 10 elements with uniq bar and foo strings.

Expected output:

[
    {
        "foo": "foo0",
        "bar": "bar"
    },
    {
        "foo": "foo1",
        "bar": "bar"
    },
    {
        "foo": "foo2",
        "bar": "bar"
    },
    {
        "foo": "foo3",
        "bar": "bar"
    },
    {
        "foo": "foo4",
        "bar": "bar"
    },
    {
        "foo": "foo",
        "bar": "bar"
    },
    {
        "foo": "foo",
        "bar": "bar996"
    },
    {
        "foo": "foo",
        "bar": "bar997"
    },
    {
        "foo": "foo",
        "bar": "bar998"
    },
    {
        "foo": "foo",
        "bar": "bar999"
    }
]

Yet in reality I see all the elements to be kept in the list. It's as if the _.uniq isn't doing anything.

I want to get a unique list of the array based on identity / equalness. All array duplicates for all properties combination shall be removed.

How can I achieve that?

k0pernikus · Accepted Answer · 2020-11-06 10:45:00Z

5

Note: I'm using lodash/fp. If you use lodash, the order of the args of _.uniqWith are switched.

When you want uniqueness for an object you can use _.uniqWith:

const withoutDupes = _.uniqWith(_.isEqual, objects);
console.log(
    JSON.stringify(withoutDupes, null, 4),
);

As to your first appraoch, keep in mind that _.uniq isn't working on a collection of objects but only works for simple arrays, e.g.:

const simpleArray = [1, 1, 1, 1, 2, 3];
console.log(_.uniq(simpleArray));

outputs:

[ 1, 2, 3 ]

edited Nov 6, 2020 at 10:45

answered Jun 7, 2018 at 10:58

k0pernikus

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