Benchmark: JavaScript spread operator vs Object.assign performance with new object in assign

Tests:

Using the spread operator
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = { ...firstObject, ...secondObject };
Using Object.assign
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = Object.assign({}, firstObject, secondObject);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using the spread operator
Using Object.assign

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/112.0.0.0 Safari/537.36

Browser/OS: Chrome 112 on Linux

View result in a separate tab

Test name	Executions per second
Using the spread operator	3553059.0 Ops/sec
Using Object.assign	8254889.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this benchmark.

**What is being compared?**

The benchmark compares two approaches for merging objects in JavaScript:

1. **Spread Operator (`...`)**: This syntax was introduced in ECMAScript 2018 (ES2018). It allows you to extract properties from an object and spread them into a new object.
2. **Object.assign()**: This is a built-in method in JavaScript that merges the properties of two or more objects into a single object.

**Options compared**

The benchmark tests the performance difference between using the spread operator (`...`) and `Object.assign()` to merge two objects: `firstObject` and `secondObject`.

**Pros and Cons of each approach**

1. **Spread Operator (`...`)**:
	* Pros:
		+ More concise and readable syntax.
		+ Allows for more flexibility in merging objects (e.g., can handle nested objects).
	* Cons:
		+ May be slower than `Object.assign()` due to the overhead of parsing the spread operator.
2. **Object.assign()**:
	* Pros:
		+ Faster execution compared to the spread operator.
		+ More traditional and widely supported syntax.
	* Cons:
		+ Less readable and less flexible syntax.

**Other considerations**

When choosing between these two approaches, consider the following:

* If readability is important and performance isn't a critical concern, use the spread operator (`...`).
* If performance is crucial and conciseness is not essential, use `Object.assign()`.

**Library and special JavaScript features**

In this benchmark, there are no specific libraries used. However, it's worth noting that the spread operator (`...`) was introduced in ECMAScript 2018 (ES2018), so older browsers or environments may not support it.

**Benchmark preparation code**

The script preparation code is empty, which means the benchmark starts with a clean slate and doesn't include any external dependencies or initialization code.

**Other alternatives**

If you're interested in exploring alternative approaches, consider the following:

1. **Object.create()**: This method creates a new object based on a provided prototype. It can be used to merge objects in a similar way to `Object.assign()`, but with more flexibility.
2. **Object.assign() with an empty object**: Using `{}` as the target object for `Object.assign()` can provide better performance than using `null` or undefined, which may cause browsers to optimize away the assignment.
3. **Array.prototype.reduce()**: This method can be used to merge objects by reducing an array of key-value pairs into a single object.

Keep in mind that these alternatives may have different trade-offs and use cases compared to the spread operator (`...`) and `Object.assign()`.

Related benchmarks:

JavaScript spread operator vs Object.assign performance with new object in assign (version: 0)

Comparing performance of: Using the spread operator vs Using Object.assign

Created: one year ago by: Guest

Jump to the latest result

Using the spread operator

Using Object.assign

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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