Benchmark: object spread vs Object.assign

Script Preparation code:

var a = {a: 1}

Tests:

object spread
var b = {...a, b: 2}
Object.assign
var c = Object.assign({}, a, {b: 2})

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
object spread
Object.assign

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36

Browser/OS: Chrome 135 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
object spread	42775248.0 Ops/sec
Object.assign	12861979.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its test cases to understand what's being tested.

**Benchmark Overview**

The benchmark compares two approaches for creating objects in JavaScript:

1. **Object Spread (`...`)**: This syntax was introduced in ECMAScript 2015 (ES6) as part of the object literal notation.
2. **Object.assign()**: This method is used to create a new object by copying properties from an existing object.

**Test Cases**

There are two test cases:

1. **"object spread"`**: The benchmark code uses the object spread syntax to create a new object `b` that inherits the properties of `a`, and then adds a new property `b: 2`.
```javascript
var b = {...a, b: 2}
```
2. **"Object.assign()"** : The benchmark code uses the `Object.assign()` method to create a new object `c` by copying properties from `a` and adding a new property `b: 2`.
```javascript
var c = Object.assign({}, a, {b: 2})
```
**Comparison**

The benchmark is testing the performance difference between these two approaches.

**Pros and Cons of Each Approach**

**Object Spread (`...`)**

Pros:

* More concise and readable syntax.
* No need to create an empty object or use `Object.create()`.

Cons:

* Can be slower due to the overhead of creating a new object using the spread operator.
* May not work as expected if the source object has non-enumerable properties.

**Object.assign()**

Pros:

* Faster execution, especially for large objects.
* Works with any type of object, including arrays and functions.

Cons:

* Requires more code to achieve the same result.
* Can be less readable due to the method call syntax.

**Library and Purpose**

In this benchmark, there is no library being used. The `Object.assign()` method is a built-in JavaScript function that is part of the ECMAScript standard.

**Special JS Feature or Syntax**

There are no special features or syntaxes being tested in this benchmark.

**Other Alternatives**

Alternative approaches to object creation include:

* Using the `Object.create()` method to create an object with a given prototype.
* Using the `{}` literal notation and manually setting properties on the resulting object.
* Using libraries like Lodash's `cloneDeep` function to clone objects.

However, these alternatives are not being tested in this benchmark.

Related benchmarks:

object spread vs Object.assign (version: 0)

Comparing performance of: object spread vs Object.assign

Created: 4 years ago by: Guest

Jump to the latest result

object spread

Object.assign

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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