Benchmark: set array index: slice vs Object.assign

Tests:

splice
var index = 2; var array = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]; var output = [ ...array.slice(0, index), 10, ...array.slice(index + 1) ];
Object.assign
var array = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]; var output = Object.assign([], array, {2: 10});

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
splice
Object.assign

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 131 on Android

View result in a separate tab

Test name	Executions per second
splice	7920754.0 Ops/sec
Object.assign	459369.7 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 Overview**

The benchmark compares two approaches to slice an array: using `array.slice(0, index)` and `Object.assign([], array, {2: 10})`. The goal is to determine which approach is faster for a specific use case.

**Options Compared**

There are two main options being compared:

1. **`array.slice(0, index)`**: This method returns a new array containing the elements before the specified index.
	* Pros:
		+ Creates a new array, avoiding modifying the original array.
		+ More predictable performance, as it only involves slicing and copying the original data.
	* Cons:
		+ May incur more overhead due to the creation of a new array.
2. **`Object.assign([], array, {2: 10})`**: This method uses `Object.assign()` to merge an object with the specified key-value pair onto another object.
	* Pros:
		+ Modifies the original array in place, which might be more efficient for large arrays.
		+ Can be faster for larger indices, as it only needs to copy a subset of the original data.
	* Cons:
		+ May modify the original array unexpectedly, depending on the context.
		+ The `Object.assign()` method itself can incur overhead due to its implementation.

**Other Considerations**

When choosing between these approaches, consider the following factors:

* **Array size and shape**: For small arrays or arrays with a limited number of elements, the difference in performance might be negligible. However, for larger arrays, the creation of a new array using `slice()` may incur more overhead.
* **Performance requirements**: If predictability and reliability are crucial, `array.slice(0, index)` might be a better choice. If speed is the primary concern, especially for large indices, `Object.assign()` could provide a performance advantage.
* **Array modification**: If you need to modify the original array in place, `Object.assign()` might be more suitable. However, if you want to avoid modifying the original array, `array.slice(0, index)` is a safer choice.

**Libraries and Special Features**

In this benchmark, no libraries are explicitly mentioned or used. However, it's worth noting that some JavaScript engines or browsers may optimize certain functions or methods differently due to their internal implementation.

**Alternatives**

If you're looking for alternatives to these approaches, consider the following:

* **`Array.prototype.splice()`**: This method modifies the original array in place and can be faster than `array.slice(0, index)` for small arrays. However, it may incur more overhead for larger arrays.
* **`Array.prototype.map()`** with `slice()`: You can use `map()` to create a new array containing only the elements before the specified index. This approach avoids modifying the original array and is often faster than using `Object.assign()`.
* **`Spread operator (`...`)**: In some cases, you can achieve similar results using the spread operator (`...`). For example: `[...array.slice(0, index), 10, ...array.slice(index + 1)]`. This approach is often faster and more readable than using `Object.assign()`.

Keep in mind that these alternatives may have different trade-offs and performance characteristics depending on the specific use case.

Related benchmarks:

set array index: slice vs Object.assign (version: 0)

Comparing performance of: splice vs Object.assign

Created: 6 years ago by: Guest

Jump to the latest result

splice

Object.assign

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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