Benchmark: JS Array Slice vs Array Spread

Tests:

Slice
const arr = [...Array(10000).keys()]; const arrClone = arr.slice();
Spread
const arr = [...Array(10000).keys()]; const arrClone = [...arr];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Slice
Spread

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.106 Safari/537.36

Browser/OS: Chrome 83 on Mac OS X 10.15.5

View result in a separate tab

Test name	Executions per second
Slice	2902.9 Ops/sec
Spread	3017.0 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 JavaScript microbenchmark and explain what's being tested.

**Benchmark Definition**

The benchmark definition is not provided in the given JSON, but we can infer its purpose from the test cases.

Two main approaches are compared:

1. **Array Slice**: This approach uses the `slice()` method to create a shallow copy of an array.
2. **Array Spread**: This approach uses the spread operator (`...`) to create a new array with a copy of the original array.

**Options Compared**

The two options are being tested for their performance, specifically:

* Which approach is faster and more efficient?
* How do the different browsers (in this case, Chrome 83) compare in terms of execution speed?

**Pros and Cons of Each Approach**

1. **Array Slice**:
	* Pros: More widely supported across browsers, often considered safer due to its explicit copying mechanism.
	* Cons: Can be slower than Array Spread for large datasets, as it creates a new array object with references to the original elements.
2. **Array Spread**:
	* Pros: Can be faster for large datasets, as it uses a more efficient copy operation, and is often used in modern JavaScript development.
	* Cons: May not work across all browsers or environments, due to variations in implementation.

**Library Usage**

There doesn't appear to be any specific library being used in this benchmark.

**Special JS Features/Syntax**

The use of the spread operator (`...`) in Array Spread is a relatively recent feature introduced in ECMAScript 2015 (ES6). It allows for creating new arrays with a copy of the original array's elements. This syntax is widely supported across modern browsers and environments, but older versions may not recognize it.

**Other Considerations**

* **Browser Variability**: The benchmark results are shown for a single browser version (Chrome 83) on a Mac OS X system. In real-world scenarios, different browsers and operating systems may exhibit varying performance characteristics.
* **Dataset Size**: The test case uses an array of size 10,000 elements, which is relatively large. This might not be representative of smaller datasets, where other factors like memory allocation or garbage collection might come into play.

**Alternatives**

Other alternatives for creating a copy of an array could include:

1. `Array.prototype.slice.call()` (or simply `.slice()`)
2. `Array.from()` with an empty array (`[]`) as the initial argument
3. `new Array(size)` followed by `fill()` to create an array of specified size

However, these alternatives might not be as efficient or readable as using the spread operator for large datasets.

In summary, this benchmark compares two approaches to creating a copy of an array: Array Slice and Array Spread. The spread operator is likely preferred due to its efficiency and modern syntax, but its usage may not work across all browsers or environments.

Related benchmarks:

JS Array Slice vs Array Spread (version: 0)

Comparing performance of: Slice vs Spread

Created: 4 years ago by: Guest

Jump to the latest result

Slice

Spread

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):