Benchmark: JavaScript Array.slice vs Array.slice(0)

Script Preparation code:

const ITERATIONS = 500000;
var index = ITERATIONS/2;
var n = Math.random();

var list = [];
for (let i = 0; i < length; i += 1) {
  list.push(Math.random());
}

Tests:

Array clone with slice(0)
const clone = list.slice(0);
Array clone with slice
const clone = list.slice();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array clone with slice(0)
Array clone with 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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I'd be happy to help explain the provided benchmark.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark for testing two different approaches to creating an array copy using `Array.slice()`. The goal is to compare the performance of these two methods: `slice(0)` and `slice()` without any arguments.

**What are being tested?**

In this benchmark, we're comparing the execution time of two methods:

1. **`Array.slice(0)`**: This method creates a shallow copy of the original array by returning a new array containing only the elements from the beginning of the original array up to (but not including) the specified length.
2. **`Array.slice()` without any arguments**: This method creates a shallow copy of the original array, similar to `slice(0)`, but it includes all elements in the original array.

**Options Compared**

The benchmark is comparing two options:

1. **Shallow Copy using `slice(0)`**: Creates a new array with only the first `length` elements from the original array.
2. **Full Copy using `slice()` without any arguments**: Creates a new array with all elements from the original array.

**Pros and Cons**

Here are some pros and cons of each approach:

*   **Shallow Copy using `slice(0)`**
    *   Pros:
        *   Faster execution time, since it only includes the first `length` elements.
        *   Less memory usage, since it doesn't create a new array with all elements.
    *   Cons:
        *   May not be suitable for arrays that need to be fully copied or modified.
*   **Full Copy using `slice()` without any arguments**
    *   Pros:
        *   Ensures a full and accurate copy of the original array, which may be necessary in certain scenarios.
        *   Easier to understand and maintain, as it creates a new array with all elements.

**Library Usage**

There is no library usage mentioned in this benchmark. The benchmark only uses native JavaScript methods.

**Special JS Features or Syntax**

There are no special JS features or syntax used in this benchmark.

**Other Considerations**

When deciding between these two approaches, consider the following factors:

*   **Memory usage**: If memory efficiency is a concern, `slice(0)` might be a better choice. However, if you need to ensure a full and accurate copy of the array, `slice()` without any arguments may be more suitable.
*   **Execution time**: If speed is critical, `slice(0)` might offer faster execution times. Nevertheless, this can depend on the specific use case and environment.

**Alternatives**

If you're looking for alternative ways to create an array copy in JavaScript, consider using:

1.  `Array.from()`: Creates a new array from an iterable.
2.  `Object.assign()` or `Array.prototype.concat()`: Copies elements from one or more arrays to a new array.
3.  `lodash` (a popular utility library): Offers various methods for creating copies of arrays, such as `_.clone()`.

Keep in mind that the choice of method depends on your specific requirements and the context in which you're working.

Related benchmarks:

JavaScript Array.slice vs Array.slice(0) (version: 0)

Comparing performance of: Array clone with slice(0) vs Array clone with slice

Created: 4 years ago by: Guest

Jump to the latest result

Array clone with slice(0)

Array clone with 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):