Run results for: Copying data; mapping vs. spreading then modifying vs. Object.assign then modifiying

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:101.0) Gecko/20100101 Firefox/101.0

Browser: Firefox 101

Operating system: Linux

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
Mapping	16935210.0 Ops/sec
spreading, then modifying	8021250.0 Ops/sec
Object.assign, then modifying	1541070.0 Ops/sec

Script Preparation code:

var data = [{
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    },
    {
        foo: {
            bar: {
                baz: "hi"
            }
        }
    }
];

Tests:

Mapping
data.map((d, i) => i=== 2 ? "replaced" : d)
spreading, then modifying
const copy = [...data]; copy[2] = "replaced";
Object.assign, then modifying
const copy = Object.assign([], data) copy[2] = "replaced";

Run results for: Copying data; mapping vs. spreading then modifying vs. Object.assign then modifiying

Mapping

spreading, then modifying

Object.assign, then modifying