Benchmark: Difference of Object.assign and spread operator to get a new reference

Script Preparation code:

myObj = {a: 1, b: 2, c: 3}

Tests:

Using Object.assign
const newObjectA = Object.assign({}, myObj)
Using spread operator
const newObjectB = {...myObj}
Using a plain initialization
const newObjectC = JSON.parse(JSON.stringify(myObj))

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using Object.assign
Using spread operator
Using a plain initialization

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

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Let's break down the provided benchmark and explain what's being tested.

**Benchmark Definition**
The benchmark is designed to compare three different approaches to create a new reference to an object in JavaScript:

1. `Object.assign()`
2. Spread operator (`{...}`)
3. A plain initialization using `JSON.parse()` (not recommended, but included for comparison)

**Options Compared**

* **Option 1: Using `Object.assign()`**
	+ Creates a shallow copy of the original object by referencing its properties.
	+ Returns an object with the same prototype as the original object.
	+ Can lead to unexpected behavior if the original object has mutable properties that are also assigned to other variables.
* **Option 2: Spread Operator (`{...}`)**
	+ Creates a shallow copy of the original object by spreading its properties into a new object.
	+ Returns an object with a separate prototype from the original object.
	+ Is more memory-efficient than `Object.assign()`.
* **Option 3: Plain Initialization using `JSON.parse()`**
	+ Not recommended, as it can lead to unexpected behavior if the original object has complex data structures or circular references.
	+ Creates a new object with a separate prototype from the original object.

**Pros and Cons**

* `Object.assign()`:
	+ Pros: easy to use, widely supported
	+ Cons: can lead to unexpected behavior, not memory-efficient
* Spread Operator (`{...}`):
	+ Pros: more memory-efficient, creates a new prototype
	+ Cons: not as widely supported as `Object.assign()`
* Plain Initialization using `JSON.parse()`:
	+ Pros: None notable
	+ Cons: not recommended due to potential unexpected behavior

**Library and Purpose**
There are no libraries used in this benchmark.

**Special JS Feature or Syntax**
The spread operator (`{...}`) is a feature introduced in ECMAScript 2018 (ES2018), but it's supported by modern browsers, including Chrome 71. The `Object.assign()` method has been part of the JavaScript standard since ECMAScript 5 (ES5).

**Other Alternatives**
For creating a new object with a specific prototype or behavior, other approaches can be used:

* For creating an object with a specific prototype: use the constructor function (e.g., `new MyConstructor()`)
* For creating an immutable object: use libraries like Immutable.js or Lodash's `createImmutable()` function
* For creating an object from an array: use the spread operator (`{...array}`)

Related benchmarks:

Difference of Object.assign and spread operator to get a new reference (version: 6)

Comparing performance of: Using Object.assign vs Using spread operator vs Using a plain initialization

Created: 7 years ago by: Registered User

Jump to the latest result

Using Object.assign

Using spread operator

Using a plain initialization

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):