Benchmark: JavaScript spread operator vs Object.assign performance without useless assignment

Tests:

Using the spread operator
const firstObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } const finalObject = { ...firstObject, ...secondObject };
Using Object.assign
const finalObject = { sampleData: 'Hello world' } const secondObject = { moreData: 'foo bar' } Object.assign(finalObject, 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: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 11_2_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.192 Safari/537.36

Browser/OS: Chrome 88 on Mac OS X 11.2.2

View result in a separate tab

Test name	Executions per second
Using the spread operator	2482476.0 Ops/sec
Using Object.assign	5658880.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into explaining the benchmark.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark on MeasureThat.net, comparing the performance of two approaches for merging objects: using the spread operator (`...`) and `Object.assign()`. The test is designed to measure which approach is more efficient without unnecessary assignments.

**Options Compared**

Two options are being compared:

1. **Using the Spread Operator (`...`):**
	* Pros:
		+ More concise and readable syntax.
		+ Does not require explicit checking for object existence or assignment.
	* Cons:
		+ Might incur additional overhead due to property iteration.
2. **Using `Object.assign()`:**
	* Pros:
		+ Established, widely supported method for merging objects.
		+ May perform better due to optimized internal implementation.
	* Cons:
		+ Requires explicit checking for object existence or assignment.

**Pros and Cons of Each Approach**

Both approaches have their trade-offs:

* Using the spread operator provides a more concise and readable syntax but might incur additional overhead due to property iteration. This can be beneficial if readability is prioritized over raw performance.
* Using `Object.assign()` offers an established, widely supported method for merging objects, potentially with optimized internal implementation, but requires explicit checking for object existence or assignment.

**Library Used**

There is no library explicitly mentioned in the provided JSON. However, it's worth noting that `Object.assign()` has been a built-in method in JavaScript since ECMAScript 2015 (ES6), making it widely supported across different browsers and environments.

**Special JS Feature/Syntax**

The benchmark utilizes the spread operator (`...`), which is a relatively new feature introduced in ECMAScript 2018 (ES2018). The spread operator allows you to expand an array or object into multiple arguments or merge objects using the `...` syntax. This feature has become widely supported across modern browsers and environments.

**Alternatives**

If you're interested in exploring alternative approaches for merging objects, consider the following options:

1. **Object.create()**: You can create a new object using `Object.create()` and then assign properties to it.
2. **Array.prototype.concat()**: You can concatenate arrays using `Array.prototype.concat()` and then convert the result back to an object.
3. **Manual Property Iteration**: You can iterate over properties of one object and manually assign them to another object.

Keep in mind that these alternatives might not be as concise or readable as the spread operator or `Object.assign()`, but they can provide a deeper understanding of how merging objects works under the hood.

Related benchmarks:

JavaScript spread operator vs Object.assign performance without useless assignment (version: 0)

Object.assign first parameter is automatically updated with the following object(s)

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

Created: 3 years ago by: Registered User

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):