Benchmark: Array add vs .unshift() 2

Script Preparation code:

var arr = [1,2,3,4]

Tests:

.unshift()
arr.unshift(42)
.concat
[42].concat(arr)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
.unshift()
.concat

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; rv:120.0) Gecko/20100101 Firefox/120.0

Browser/OS: Firefox 120 on Linux

View result in a separate tab

Test name	Executions per second
.unshift()	538794.0 Ops/sec
.concat	128.1 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**Benchmark Definition**

The benchmark is testing two approaches for adding an element to the end of an array:

1. `.unshift()`
2. `.concat` with an array literal `[42]`

**Options Compared**

Here are the options being compared, along with their pros and cons:

* `.unshift()`:
	+ Pros: O(1) time complexity, modifies the original array in place.
	+ Cons: Can be slower than other methods due to its internal implementation details (e.g., it involves shifting elements).
* `.concat` with an array literal `[42]`:
	+ Pros: Creates a new array and returns it, which can be faster for large arrays.
	+ Cons: O(1) time complexity in JavaScript, but creates a new array, which can lead to increased memory usage.

**Library and Purpose**

There is no explicit library mentioned in the benchmark definition or test cases. However, `Array.prototype.unshift()` and `Array.prototype.concat()` are built-in methods of the JavaScript Array prototype.

**Special JS Features/Syntax**

No special JavaScript features or syntax are used in this benchmark. It only involves standard JavaScript array operations.

**Other Alternatives**

Other alternatives for adding an element to the end of an array include:

* `push()`: Creates a new array and returns it, similar to `.concat()`, but with O(1) time complexity.
* `Array.prototype.splice()` with the `0` index: Modifies the original array in place, similar to `.unshift()`.
* Creating a new array using the `[]` syntax and then assigning the result of the operation to the original array (e.g., `[...arr, 42]`).

The choice of alternative depends on the specific use case and performance requirements.

**Benchmark Preparation Code**

The preparation code provided is:
```javascript
var arr = [1,2,3,4];
```
This creates an initial array `arr` with four elements. The benchmark definition then performs the specified operation (e.g., `.unshift(42)` or `[42].concat(arr)`).

**Individual Test Cases**

The test cases are defined as an array of objects, each containing:

* A `BenchmarkDefinition`: a string representing the JavaScript code to execute (e.g., `"arr.unshift(42)"`).
* A `TestName`: a string representing the name of the test case (e.g., ".unshift()").

These test cases allow users to create and run multiple benchmarks, comparing different approaches for adding an element to the end of an array.

Related benchmarks:

Array add vs .unshift() 2 (version: 0)

Comparing performance of: .unshift() vs .concat

Created: one year ago by: Guest

Jump to the latest result

.unshift()

.concat

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):