Benchmark: JavaScript spread operator vs Object.assign performance fixed 2

Script Preparation code:

var firstObject = { sampleData: 'Hello world' }
var secondObject = { moreData: 'foo bar' }

Tests:

Using the spread operator
const finalObject = { ...firstObject, ...secondObject };
Using Object.assign
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: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36

Browser/OS: Chrome 114 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Using the spread operator	5050028.5 Ops/sec
Using Object.assign	7391320.0 Ops/sec

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

LLMs can make mistakes. Check important info.

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

The provided JSON represents a JavaScript microbenchmarking test case, specifically comparing the performance of two approaches: using the spread operator (`...`) and `Object.assign()` to merge two objects into a single object.

**Options Compared**

The two options being compared are:

1. Using the spread operator (`...`):
```javascript
const finalObject = { ...firstObject, ...secondObject };
```
2. Using `Object.assign()`:
```javascript
const finalObject = Object.assign({}, firstObject, secondObject);
```

**Pros and Cons of Each Approach**

1. **Using the spread operator (`...`):**
	* Pros:
		+ More concise and readable code.
		+ Expresses intent clearly that two objects are being merged.
	* Cons:
		+ May be slower due to the overhead of creating a new array-like object.
2. **Using `Object.assign()`:**
	* Pros:
		+ Can be faster since it avoids creating a new array-like object.
	* Cons:
		+ Requires more code and is less concise than using the spread operator.
		+ May not express intent as clearly.

**Other Considerations**

Both approaches have trade-offs between readability, conciseness, and performance. In general, using the spread operator can make your code more readable and maintainable, but may incur a slight performance penalty. Using `Object.assign()` is more concise, but less readable and may be slower due to its overhead.

**Library and Special JS Features**

In this benchmark, no libraries or special JavaScript features are being used beyond what's built into the standard library. The spread operator was introduced in ECMAScript 2018 (ES2018) and `Object.assign()` has been available since ES5.

**Alternatives**

If you need to merge objects frequently, other alternatives include:

1. Using a library like Lodash (`_`.merge()) or Underscore.js (`_.extend()`) which provide more concise ways to merge objects.
2. Using the `Object.create()` method and then assigning properties to it:
```javascript
const finalObject = Object.create(firstObject);
finalObject.sampleData = 'Hello world';
finalObject.moreData = 'foo bar';
```
However, these alternatives may not be as readable or maintainable as using the spread operator or `Object.assign()`.

Related benchmarks:

JavaScript spread operator vs Object.assign performance fixed 2 (version: 0)

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

Created: 3 years ago by: Guest

Jump to the latest result

Using the spread operator

Using 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):