Benchmark: Array remove item using Array.concat vs array spread

Script Preparation code:

var a = new Array(1000000).fill(undefined).map((_, i) => i)

Tests:

Using array.concat
var b = a.slice(0, 500000).concat(a.slice(500001))
Using array.spread
var b = [...a.slice(0, 500000), ...a.slice(500001)]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Using array.concat
Using array.spread

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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Let's break down the provided benchmark and explain what's being tested.

**Benchmark Definition**

The benchmark is designed to test two different approaches for removing an item in the middle of an array of length 1,000,000. The goal is to compare the performance of using `Array.concat` versus `array spread` (also known as destructuring) to remove an element from the middle of the array.

**Script Preparation Code**

The script preparation code creates a large array `a` with 1,000,000 elements, where each element is set to `undefined`. The purpose of this code is to create a large, empty array that will be used for testing.

**Html Preparation Code**

There is no HTML preparation code provided, which means that the benchmark does not take into account any DOM-related operations or other non-array-related aspects.

**Individual Test Cases**

The test cases are designed to compare two different approaches:

1. **Using `Array.concat`**: This approach uses the `concat` method to remove an element from the middle of the array. Specifically, it creates a new array `b` by concatenating two parts: the first half of the original array (`a.slice(0, 500000)`) and the second half of the array (starting from index 500001).
2. **Using `array spread`**: This approach uses destructuring to remove an element from the middle of the array. Specifically, it creates a new array `b` by spreading two parts: the first half of the original array (`a.slice(0, 500000)`) and the second half of the array (starting from index 500001).

**Pros and Cons**

Here's a brief summary of the pros and cons of each approach:

* **Using `Array.concat`**:
	+ Pros: Can be more readable and easier to understand for some developers.
	+ Cons: Creates a new array, which can lead to performance issues if not done efficiently (e.g., using `slice` instead of indexing).
* **Using `array spread`**:
	+ Pros: More concise and often faster than concatenation methods.
	+ Cons: May be less readable for developers who are not familiar with destructuring.

**Library Usage**

There is no explicit library usage in this benchmark, but it does use the built-in `Array.prototype.slice()` method to create a new array slice from the original array. The `array spread` approach uses the spread operator (`...`) to create a new array by spreading two parts together.

**Special JS Features or Syntax**

The benchmark does not use any special JavaScript features or syntax beyond what is commonly used in modern JavaScript development. No ES6+ features, such as async/await, classes, or modules, are used.

**Alternatives**

If you wanted to rewrite this benchmark with alternative approaches, here are some options:

* Using `splice()` instead of `concat` or spread.
* Using a library like Lodash's `removeAt()` function.
* Using a different data structure, such as a Set or Map, for the removal operation.

Keep in mind that the performance differences between these alternatives may vary depending on the specific use case and hardware.

Related benchmarks:

Array remove item using Array.concat vs array spread (version: 0)

Remove an item in the middle of an array of length 1000000 using either Array.concat or array spread

Comparing performance of: Using array.concat vs Using array.spread

Created: 5 years ago by: Guest

Jump to the latest result

Using array.concat

Using array.spread

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):