Benchmark: spread vs concat vs unshift 213124

Script Preparation code:

var array = [1,2,3];
var array2 = [-1,-2,-3];

Tests:

arrayUnshift123
array.unshift(...array2);
arrayConcat123
array = array2.concat(array)
arraySpread123
array = [...array2, ...array]
arrayUnshiftApply
array.unshift.apply(array, array2)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
arrayUnshift123
arrayConcat123
arraySpread123
arrayUnshiftApply

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks!

**Benchmark Overview**

The provided JSON represents a benchmark that tests the performance of three ways to concatenate or append elements to an array in JavaScript:

1. `unshift()`
2. `concat()`
3. `spread` (using the spread operator, `...`)

These methods are commonly used in JavaScript for array manipulation and can have significant performance implications.

**Method Comparison**

The test cases compare the performance of these three methods:

* `array.unshift(...array2)`: This method uses the `unshift()` method to add elements at the beginning of the array.
* `array = array2.concat(array)`: This method uses the `concat()` method to create a new array by concatenating `array2` and `array`.
* `array = [...array2, ...array]`: This method uses the spread operator (`...`) to create a new array by spreading elements from `array2` and `array`.

**Pros and Cons of Each Approach**

Here are some pros and cons for each approach:

1. **`unshift()`**:
	* Pros: Can be more efficient than `concat()` when appending multiple elements, as it only requires a single operation.
	* Cons: Can be slower than `concat()` for small arrays or when appending a single element.
2. **`concat()`**:
	* Pros: Generally faster and more reliable than `unshift()`, especially for larger arrays.
	* Cons: Creates a new array, which can be memory-intensive.
3. **`spread` (using `...`)**:
	* Pros: Concise and expressive syntax, easy to read and maintain.
	* Cons: Can be slower than `concat()` due to the overhead of creating a new array.

**Library Usage**

None of the test cases use any external libraries.

**Special JS Features or Syntax**

The spread operator (`...`) is used in one of the test cases (`array = [...array2, ...array]`). The spread operator is a relatively recent addition to JavaScript (introduced in ECMAScript 2015) and allows for concise array creation by spreading elements from an existing array.

**Other Alternatives**

Some alternative approaches to appending elements to an array include:

* Using `push()` method: `array.push(...array2)`
* Using `slice()` method: `array = [...array.slice(0), ...array2]`
* Using `Array.prototype.concat.call()` method: `array = Array.prototype.concat.call(array, array2)`

However, these alternatives may not be as efficient or concise as the three methods being tested.

I hope this explanation helps!

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.100 Safari/537.36

Browser/OS: Chrome 76 on Windows

View result in a separate tab

Test name	Executions per second
arrayUnshift123	11360.7 Ops/sec
arrayConcat123	397.1 Ops/sec
arraySpread123	95.4 Ops/sec
arrayUnshiftApply	3666.2 Ops/sec

Related benchmarks:

spread vs concat vs unshift 213124 (version: 0)

spread vs concat vs unshift

Comparing performance of: arrayUnshift123 vs arrayConcat123 vs arraySpread123 vs arrayUnshiftApply

Created: 5 years ago by: Guest

Jump to the latest result

arrayUnshift123

arrayConcat123

arraySpread123

arrayUnshiftApply

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):