Benchmark: JavaScript spread operator vs Object.assign performance 22478

Script Preparation code:

const obj1 = { a: "a" };
const obj2 = { b: "b" };

window.obj1 = obj1;
window.obj2 = obj2;

Tests:

Spread operator
const finalObject = { ...obj1, d: "b", ...obj2 };
Object.assign
const finalObject = Object.assign({ }, obj1, { d: "b" }, obj2);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread operator
Object.assign

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this JavaScript microbenchmark.

**Benchmark Overview**

The benchmark compares the performance of two approaches to merge objects:

1. The spread operator (`...` syntax)
2. `Object.assign()`

**Options Compared**

The benchmark tests two options for merging objects:

a. Using the spread operator (`...` syntax) to create a new object with properties from both `obj1` and `obj2`.
b. Using `Object.assign()` to merge objects.

**Pros and Cons of Each Approach**

**Spread Operator (using `...` syntax)**

Pros:

* More concise and readable code
* Efficient, as it only creates a shallow copy of the source object
* Can handle nested objects with ease

Cons:

* Not supported in older browsers or environments that don't support ES6+
* May not be optimized for performance in certain scenarios (e.g., when dealing with very large datasets)

**Object.assign()**

Pros:

* Widely supported across modern browsers and environments
* Well-documented and widely understood
* Can handle nested objects with ease

Cons:

* Less concise and readable code compared to the spread operator
* Creates a shallow copy of the source object, which can lead to unexpected behavior if one of the objects contains circular references.

**Library Used**

In this benchmark, `Object.assign()` is used as the built-in JavaScript function for merging objects. No external libraries are required.

**Special JS Features or Syntax**

The benchmark uses ES6+ features such as the spread operator (`...` syntax) and template literals. If your team is using an older version of JavaScript that doesn't support these features, you may need to modify the benchmark code accordingly.

**Other Alternatives**

If you're looking for alternative approaches to merging objects in JavaScript, consider the following options:

1. **Lodash.merge()**: A popular utility library that provides a comprehensive set of functions for working with data structures.
2. **Underscore.js.merge()**: Another widely-used utility library that offers an efficient and flexible way to merge objects.
3. **JSON merge libraries**: There are several third-party libraries available that specialize in merging JSON objects, such as json-merge or json-merge.

Keep in mind that the spread operator (`...` syntax) is now a standard feature of modern JavaScript, making it a popular choice for merging objects.

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Linux; Android 13; Pixel 4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/106.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 106 on Android

View result in a separate tab

Test name	Executions per second
Spread operator	442213.0 Ops/sec
Object.assign	973906.4 Ops/sec

Related benchmarks:

JavaScript spread operator vs Object.assign performance 22478 (version: 0)

Comparing performance of: Spread operator vs Object.assign

Created: 2 years ago by: Guest

Jump to the latest result

Spread operator

Object.assign

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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