Benchmark: Array.prototype.slice vs spread operator for Array copy

Script Preparation code:

var arr = [];
for (let i;i<1000000;i++){
	arr.push(i);
}

Tests:

Array.prototype.slice
var other = arr.slice();
spread operator
var other = [ ...arr ]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.prototype.slice
spread operator

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.159 Safari/537.36

Browser/OS: Chrome 92 on Windows

View result in a separate tab

Test name	Executions per second
Array.prototype.slice	7912726.5 Ops/sec
spread operator	7474423.5 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 benchmark and explain what's being tested.

**Benchmark Overview**

The test is designed to compare two approaches for creating an array copy: `Array.prototype.slice()` and the spread operator (`...`). The benchmark aims to determine which method is faster and more efficient.

**Options Compared**

Two options are compared:

1. **`Array.prototype.slice()`**: This is a traditional way of creating an array copy by using the `slice()` method on the original array.
2. **Spread Operator (`...`)**: This is the new ES6 syntax for creating an array copy by spreading the elements of an existing array.

**Pros and Cons**

Here are some pros and cons of each approach:

* **`Array.prototype.slice()`**:
	+ Pros:
		- Well-established and widely supported.
		- Can be used to create a shallow copy of an array, which can be useful in certain scenarios.
	+ Cons:
		- May not be as efficient as the spread operator for large arrays.
		- Requires calling the `slice()` method, which can add overhead.
* **Spread Operator (`...`)**:
	+ Pros:
		- More concise and expressive than the traditional `slice()` approach.
		- Can create a deep copy of an array by using the spread operator with an object (e.g., `{ ...arr }`).
	+ Cons:
		- May not be as widely supported or understood as the traditional `slice()` method.
		- Can be slower than the `slice()` approach for very large arrays.

**Library**

The benchmark doesn't use any external libraries. However, it does rely on the built-in JavaScript functionality for array manipulation.

**Special JS Feature/Syntax**

This benchmark uses a modern JavaScript feature: the spread operator (`...`). The spread operator was introduced in ECMAScript 2015 (ES6) and has since become a standard part of the language.

**Other Considerations**

When running this benchmark, you may want to consider factors such as:

* Array size: The benchmark measures performance across different array sizes. You can experiment with varying array sizes to see how each approach scales.
* Browser/Platform differences: As shown in the latest benchmark results, browser and platform variations can impact performance. Running the benchmark on multiple platforms and browsers can help you understand these differences.

**Other Alternatives**

If you're interested in exploring alternative approaches for creating an array copy, here are a few options:

1. **`Array.from()`**: This method creates a new array from an iterable or an array-like object.
2. **`Array.prototype.concat()`**: This method concatenates multiple arrays into a single array.
3. **Using `Buffer`**: For very large arrays, using `Buffer` can provide better performance.

Keep in mind that each approach has its own trade-offs and use cases. When choosing an approach, consider the specific requirements of your project and the characteristics of your data.

Related benchmarks:

Array.prototype.slice vs spread operator for Array copy (version: 0)

Compare the new ES6 spread operator with the traditional slice() method

Comparing performance of: Array.prototype.slice vs spread operator

Created: 3 years ago by: Guest

Jump to the latest result

Array.prototype.slice

spread operator

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):