Benchmark: shallow copy of 6M elements array

Script Preparation code:

var arr = new Array(6000000).fill(0.1)
var a = []

Tests:

spread copy
a = [...arr]
slice
a = arr.slice()

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
spread copy
slice

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the provided benchmark definition and test cases to understand what's being tested.

**Benchmark Definition**

The benchmark is designed to measure the performance of creating a shallow copy of an array with 6 million elements in JavaScript. The array is initialized using `new Array(6000000).fill(0.1)`, which creates an array filled with 0.1 values.

**Script Preparation Code**

Before running the test, this code sets up the initial condition:
```javascript
var arr = new Array(6000000).fill(0.1)
var a = []
```
This line initializes the `arr` variable with 6 million elements, each containing the value 0.1. The `a` variable is left uninitialized.

**Html Preparation Code**

There's no HTML preparation code provided, which means that the benchmark only focuses on JavaScript performance.

**Test Cases**

Two test cases are defined:

1. **Spread Copy**
```javascript
Benchmark Definition: a = [...arr]
```
This test creates a new array `a` by spreading the elements of `arr`. The `[...arr]` syntax is called the spread operator and is used to create a new array with a subset of the elements from an existing array.

2. **Slice**
```javascript
Benchmark Definition: a = arr.slice()
```
This test creates a new array `a` by slicing `arr`, which means taking a subset of the array's elements.

**Library Used**

In both test cases, no specific libraries are used beyond what's already part of the JavaScript standard library. However, some modern browsers may enable additional features or polyfills for certain syntaxes.

**Special JS Feature/Syntax**

* **Spread Operator**: The spread operator (`[...arr]`) was introduced in ECMAScript 2015 (ES6) and allows creating new arrays by spreading elements from an existing array.
* **Slice Method**: The `slice()` method is a built-in method in JavaScript that allows taking a subset of the array's elements.

**Pros and Cons**

Here are some pros and cons for each approach:

* **Spread Copy**
	+ Pros: Can create a new array with a shallow copy of the original array's elements, which can be more efficient than using `slice()`.
	+ Cons: May have better performance due to its native implementation.
* **Slice**
	+ Pros: More widely supported and has been around for longer, so it might be considered a safer choice.
	+ Cons: May not be as efficient as the spread operator.

**Other Alternatives**

Some alternative ways to create a shallow copy of an array in JavaScript include:

* Using `Array.prototype.slice.call()`:
```javascript
a = Array.prototype.slice.call(arr)
```
* Using `Array.prototype.slice().slice()` (not recommended, as it creates two unnecessary arrays):
```javascript
a = arr.slice().slice()
```
It's worth noting that some other libraries or frameworks might provide additional methods for creating shallow copies of arrays.

Overall, the benchmark measures the performance difference between using the spread operator and the `slice()` method to create a shallow copy of an array.

Related benchmarks:

shallow copy of 6M elements array (version: 0)

Comparing performance of: spread copy vs slice

Created: 2 years ago by: Guest

Jump to the latest result

spread copy

slice

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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