Benchmark: Copy Array - MeasureThat.net

Script Preparation code:

var len = 1000*1000;
var arr = new Array(len);

Tests:

Spread
var arr2 = [...arr];
Slice
var arr2 = arr.slice();
Slice(0)
var arr2 = arr.slice(0);
concat
var arr2 = arr.concat();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread
Slice
Slice(0)
concat

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 7 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/140.0.0.0 Safari/537.36

Browser/OS: Chrome 140 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Spread	1459.1 Ops/sec
Slice	5953.3 Ops/sec
Slice(0)	5894.7 Ops/sec
concat	5853.6 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition**

The provided JSON represents a benchmark named "Copy Array". The benchmark measures the speed of array cloning, which is essential in various scenarios such as data processing, algorithm optimization, and performance-critical code.

**Script Preparation Code**

The script preparation code initializes an array with a length of 1 million elements: `var len = 1000*1000;\r\nvar arr = new Array(len);`. This ensures that the benchmark is run with a large, consistent array size.

**Html Preparation Code**

There is no HTML preparation code provided in this benchmark. The focus is solely on the JavaScript code.

**Test Cases**

The benchmark consists of four test cases:

1. **Spread**: `var arr2 = [...arr];`
2. **Slice**: `var arr2 = arr.slice();`
3. **Slice(0)**: `var arr2 = arr.slice(0);`
4. **Concat**: `var arr2 = arr.concat();`

These test cases compare the performance of different methods for cloning an array.

**Options Compared**

Each test case compares the performance of a specific method:

* Spread (`[...arr]`)
* Slice (`arr.slice()`)
* Slice with a starting index (`arr.slice(0)`)
* Concat (`arr.concat()`)

**Pros and Cons**

Here's a brief overview of each approach:

* **Spread**: Creates a new array by spreading the elements of `arr` into an array. Pros: concise, modern syntax. Cons: can be slower due to the overhead of creating a new array.
* **Slice**: Returns a shallow copy of `arr` from the specified index to the end of the array. Pros: efficient for large arrays, as it only copies the needed elements. Cons: returns a reference to the original array, which might not be desirable in some cases.
* **Slice(0)**: Similar to Slice, but starts from the beginning of the array. Pros: identical performance to Slice for arrays with no gaps. Cons: unnecessary for this use case.
* **Concat**: Returns a new array that is the concatenation of `arr` and an empty array. Pros: creates a new, self-contained array. Cons: slower than Slice due to the overhead of creating a new array.

**Library Usage**

There are no libraries explicitly mentioned in the benchmark definition or test cases.

**Special JS Features/Syntax**

None of the test cases use any special JavaScript features or syntax beyond what's considered standard for modern browsers (ECMAScript 2015+).

**Other Alternatives**

If you're interested in optimizing array cloning, consider using:

* `Array.from(arr)`: A modern method that creates a new array from an iterable.
* `Array.prototype.map()`: Can be used to create a new array by mapping over the original array.
* Native WebAssembly (WASM) or other low-level optimizations for performance-critical code.

Keep in mind that these alternatives might have trade-offs in terms of readability, maintainability, and compatibility with older browsers.

Related benchmarks:

Copy Array (version: 0)

Speed of array cloning

Comparing performance of: Spread vs Slice vs Slice(0) vs concat

Created: 9 years ago by: Guest

Jump to the latest result

Spread

Slice

Slice(0)

concat

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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