Benchmark: copy an array 3232

Script Preparation code:

var arr = [{name:'a', age:2}, {name:'b', age:23}, {name:'c', age:22}]

Tests:

spread
arr2 = [...arr]
from
arr2 = Array.from(arr)
concat array
arr2 = [].concat(arr)
slice
arr2 = arr.slice(0)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
spread
from
concat array
slice

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and benchmark preparation code to understand what is being tested.

**Benchmark Definition:**
The `copy_an_array_3232` benchmark is defined with three JavaScript arrays of different sizes (3, 32, and 32 again) and their corresponding preparations. The script preparation code simply defines an array with three objects, while the HTML preparation code is empty. This suggests that the benchmark is primarily testing the performance of copying an array.

**Individual Test Cases:**
The individual test cases define four different approaches to copy the original `arr` array:

1.  **Spread Operator (`arr2 = [...arr]`)**: This approach uses the spread operator (three dots) to create a new array by spreading the elements of `arr`. This is a modern JavaScript feature introduced in ECMAScript 2018.
2.  **Array.from() Method (`arr2 = Array.from(arr)`)**: This approach uses the `Array.from()` method, which creates a new array from an iterable or an array-like object. This is another modern JavaScript feature introduced in ECMAScript 2015.
3.  **concat() Method (`arr2 = [].concat(arr)`)**: This approach creates a new array and then concatenates the original `arr` using the `concat()` method. This is a more traditional approach to array copying, but it can be less efficient due to the overhead of creating an additional array.
4.  **slice() Method (`arr2 = arr.slice(0)`)**: This approach uses the `slice()` method to create a shallow copy of the original `arr`. The `slice()` method returns a new array that includes a subset of elements from the original array, starting at the specified index (in this case, 0) and going until the end.

**Comparison and Pros/Cons:**
Here's a brief comparison and analysis of each approach:

*   **Spread Operator (`arr2 = [...arr]`)**:
    *   Pros: Efficient, modern, and concise.
    *   Cons: May not be supported in older browsers or environments that don't have ECMAScript 2018 support.
*   **Array.from() Method (`arr2 = Array.from(arr)`)**:
    *   Pros: Wide browser support, relatively efficient.
    *   Cons: Requires an additional method call and may incur overhead due to the creation of a new array.
*   **concat() Method (`arr2 = [].concat(arr)`)**:
    *   Pros: Wide browser support, simple implementation.
    *   Cons: Can be less efficient due to the overhead of creating an additional array, especially for large arrays.
*   **slice() Method (`arr2 = arr.slice(0)`)**:
    *   Pros: Efficient and straightforward, suitable for most use cases.
    *   Cons: Creates a shallow copy, which might not be desirable in some situations.

**Library Usage:**
None of the test cases explicitly use any external libraries or frameworks. However, it's worth noting that `Array.from()` is built into the JavaScript language and doesn't require an additional library.

**Special JS Feature/Syntax:**
The spread operator (`arr2 = [...arr]`) uses a modern JavaScript feature introduced in ECMAScript 2018. This syntax is supported by most modern browsers but might not work in older environments without additional polyfills or support.

**Other Alternatives:**

*   **Array.prototype.copy()` Method (ES6+): If you need to copy an array and want a more efficient solution, consider using the `copy()` method introduced in ECMAScript 2019.
*   **lodash.cloneDeep() Function (Lodash library)**: If you're not concerned about browser support or prefer a more functional programming approach, Lodash's `cloneDeep()` function can be used to create a deep copy of an array.

Keep in mind that these alternatives might not be necessary depending on your specific use case and target browsers.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:89.0) Gecko/20100101 Firefox/89.0

Browser/OS: Firefox 89 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
spread	13843865.0 Ops/sec
from	5547912.5 Ops/sec
concat array	10415646.0 Ops/sec
slice	17195176.0 Ops/sec

Related benchmarks:

copy an array 3232 (version: 1)

Comparing performance of: spread vs from vs concat array vs slice

Created: 3 years ago by: Registered User

Jump to the latest result

spread

from

concat array

slice

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 28 days ago):