Benchmark: Merge two arrays - Array.prototype.concat vs spread operator

Tests:

Array.prototype.concat
var params = [ "hello", true, 7 ]; var other = [ 1, 2 ] other = other.concat(params);
spread operator
var params = [ "hello", true, 7 ] var other = [ 1, 2, ...params ] var other2 = [ ...other, ...params ]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.prototype.concat
spread operator

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; rv:120.0) Gecko/20100101 Firefox/120.0

Browser/OS: Firefox 120 on Mac OS X 10.15

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Test name	Executions per second
Array.prototype.concat	21375238.0 Ops/sec
spread operator	10682113.0 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.

**Benchmark Overview**

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks. The goal of this particular benchmark is to compare the performance of two approaches for merging arrays: `Array.prototype.concat` vs the new ES6 spread operator (`...`).

**Script Preparation Code**

The provided "Script Preparation Code" section is empty, which means that MeasureThat.net will automatically generate a script for the test case. The script will contain the benchmark definition and any necessary setup.

**Html Preparation Code**

Similarly, the "Html Preparation Code" section is also empty, indicating that MeasureThat.net will create an HTML page with the necessary elements for the test to run.

**Individual Test Cases**

There are two individual test cases:

1. **Array.prototype.concat**
```javascript
var params = [ "hello", true, 7 ];
var other = other.concat(params);
```
This test case uses the `concat` method to merge an array `params` with another array `other`. The purpose of this test is to evaluate the performance of the `concat` method.

2. **Spread Operator**
```javascript
var params = [ "hello", true, 7 ];
var other = [ 1, 2 ];
other = [...other, ...params];
```
This test case uses the spread operator (`...`) to merge an array `params` with another array `other`. The purpose of this test is to evaluate the performance of the new ES6 spread operator.

**Library and Purpose**

There are no specific libraries used in these benchmark cases. However, MeasureThat.net likely relies on JavaScript's built-in functionality for these tests.

**Special JS Features or Syntax**

The use of the spread operator (`...`) is a relatively recent addition to JavaScript, introduced in ECMAScript 2015 (ES6). The `concat` method has been part of JavaScript since its inception. The spread operator provides a concise way to merge arrays and objects, but it may have slightly different performance characteristics compared to traditional methods.

**Pros and Cons**

Here are some pros and cons for each approach:

* **Array.prototype.concat**
	+ Pros:
		- Wide browser support (all versions of JavaScript)
		- Familiarity among developers
	+ Cons:
		- May be slower than the spread operator in modern browsers
		- Can lead to unexpected behavior if not used correctly (e.g., modifying the original array)
* **Spread Operator**
	+ Pros:
		- More concise and readable code
		- Often faster than `concat` in modern browsers
	+ Cons:
		- Less familiar among older developers
		- May not work as expected in some edge cases (e.g., merging objects)

**Other Alternatives**

Other alternatives for merging arrays include:

* Using `Array.prototype.push.apply()` or `Array.prototype.splice()`
* Using a library like Lodash's `merge` function

Keep in mind that the performance differences between these methods may be negligible in most real-world scenarios. The choice of method often comes down to personal preference, code readability, and specific use cases.

I hope this explanation helps software engineers understand the benchmark and its test cases!

Related benchmarks:

Merge two arrays - Array.prototype.concat vs spread operator (version: 0)

Compare the new ES6 spread operator with the traditional concat() method

Comparing performance of: Array.prototype.concat vs spread operator

Created: 2 years ago by: Guest

Jump to the latest result

Array.prototype.concat

spread operator

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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