Object.assign vs object spread operator [duplicate]

Question

I'm always undecided if I should use the Object.assign

const options = Object.assign({}, defaultOptions, localOptions);

or the object spread operator

const options = {...defaultOptions, ...localOptions};

when considering the performance impact?

Answer 1

TLDR: for small objects, i think they perform similarly

I did some small test using jest.

these all my codes example are from JSON Data set example

// example 4
const optionsA = {
    "id": "0001",
    "type": "donut",
    "name": "Cake",
    "ppu": 0.55,
    "batters":
        {
            "batter":
                [
                    { "id": "1001", "type": "Regular" },
                    { "id": "1002", "type": "Chocolate" },
                    { "id": "1003", "type": "Blueberry" },
                    { "id": "1004", "type": "Devil's Food" }
                ]
        },
    "topping":
        [
            { "id": "5001", "type": "None" },
            { "id": "5002", "type": "Glazed" },
            { "id": "5005", "type": "Sugar" },
            { "id": "5007", "type": "Powdered Sugar" },
            { "id": "5006", "type": "Chocolate with Sprinkles" },
            { "id": "5003", "type": "Chocolate" },
            { "id": "5004", "type": "Maple" }
        ]
}

// example 8
const optionsB = {
    "items":
        {
            "item":
                [
                    {
                        "id": "0001",
                        "type": "donut",
                        "name": "Cake",
                        "ppu": 0.55,
                        "batters":
                            {
                                "batter":
                                    [
                                        { "id": "1001", "type": "Regular" },
                                        { "id": "1002", "type": "Chocolate" },
                                        { "id": "1003", "type": "Blueberry" },
                                        { "id": "1004", "type": "Devil's Food" }
                                    ]
                            },
                        "topping":
                            [
                                { "id": "5001", "type": "None" },
                                { "id": "5002", "type": "Glazed" },
                                { "id": "5005", "type": "Sugar" },
                                { "id": "5007", "type": "Powdered Sugar" },
                                { "id": "5006", "type": "Chocolate with Sprinkles" },
                                { "id": "5003", "type": "Chocolate" },
                                { "id": "5004", "type": "Maple" }
                            ]
                    }

                ]
        }
}

module.exports = {optionsA, optionsB}

this is Assign.test.js

const { optionsA, optionsB } = require("./Options");

test('jest assign test', () => {
  let options = Object.assign({}, optionsA,optionsB);
  expect(options).toEqual({
    "id": "0001",
    "type": "donut",
    "name": "Cake",
    "ppu": 0.55,
    "batters":
        {
            "batter":
                [
                    { "id": "1001", "type": "Regular" },
                    { "id": "1002", "type": "Chocolate" },
                    { "id": "1003", "type": "Blueberry" },
                    { "id": "1004", "type": "Devil's Food" }
                ]
        },
    "topping":
        [
            { "id": "5001", "type": "None" },
            { "id": "5002", "type": "Glazed" },
            { "id": "5005", "type": "Sugar" },
            { "id": "5007", "type": "Powdered Sugar" },
            { "id": "5006", "type": "Chocolate with Sprinkles" },
            { "id": "5003", "type": "Chocolate" },
            { "id": "5004", "type": "Maple" }
    ],
    "items":
        {
            "item":
                [
                    {
                        "id": "0001",
                        "type": "donut",
                        "name": "Cake",
                        "ppu": 0.55,
                        "batters":
                            {
                                "batter":
                                    [
                                        { "id": "1001", "type": "Regular" },
                                        { "id": "1002", "type": "Chocolate" },
                                        { "id": "1003", "type": "Blueberry" },
                                        { "id": "1004", "type": "Devil's Food" }
                                    ]
                            },
                        "topping":
                            [
                                { "id": "5001", "type": "None" },
                                { "id": "5002", "type": "Glazed" },
                                { "id": "5005", "type": "Sugar" },
                                { "id": "5007", "type": "Powdered Sugar" },
                                { "id": "5006", "type": "Chocolate with Sprinkles" },
                                { "id": "5003", "type": "Chocolate" },
                                { "id": "5004", "type": "Maple" }
                            ]
                    }

                ]
        }
  })
})

this is Spread.test.js

const { optionsA, optionsB } = require("./Options");

test('jest spread test', () => {
  let options = {...optionsA,...optionsB};
  expect(options).toEqual({
    "id": "0001",
    "type": "donut",
    "name": "Cake",
    "ppu": 0.55,
    "batters":
        {
            "batter":
                [
                    { "id": "1001", "type": "Regular" },
                    { "id": "1002", "type": "Chocolate" },
                    { "id": "1003", "type": "Blueberry" },
                    { "id": "1004", "type": "Devil's Food" }
                ]
        },
    "topping":
        [
            { "id": "5001", "type": "None" },
            { "id": "5002", "type": "Glazed" },
            { "id": "5005", "type": "Sugar" },
            { "id": "5007", "type": "Powdered Sugar" },
            { "id": "5006", "type": "Chocolate with Sprinkles" },
            { "id": "5003", "type": "Chocolate" },
            { "id": "5004", "type": "Maple" }
    ],
    "items":
        {
            "item":
                [
                    {
                        "id": "0001",
                        "type": "donut",
                        "name": "Cake",
                        "ppu": 0.55,
                        "batters":
                            {
                                "batter":
                                    [
                                        { "id": "1001", "type": "Regular" },
                                        { "id": "1002", "type": "Chocolate" },
                                        { "id": "1003", "type": "Blueberry" },
                                        { "id": "1004", "type": "Devil's Food" }
                                    ]
                            },
                        "topping":
                            [
                                { "id": "5001", "type": "None" },
                                { "id": "5002", "type": "Glazed" },
                                { "id": "5005", "type": "Sugar" },
                                { "id": "5007", "type": "Powdered Sugar" },
                                { "id": "5006", "type": "Chocolate with Sprinkles" },
                                { "id": "5003", "type": "Chocolate" },
                                { "id": "5004", "type": "Maple" }
                            ]
                    }

                ]
        }
  })
})

And when i do these test, they have similar time doing the work: