Benchmark: unshift vs clone array

Script Preparation code:

var itemsArray = [];

for (let i = 0; i < 100000; i++) {
	itemsArray.push(i)
}

Tests:

unshift
console.log('unshift ', itemsArray.unshift('olololol'))
spread
console.log('spread ', ['123231232312',...itemsArray])

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
unshift
spread

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases to understand what is being tested.

**Benchmark Definition JSON**

The `Script Preparation Code` section creates an array of 100,000 integers using a `for` loop and pushes each value onto the `itemsArray`. This array will be used as input for both the "unshift" and "spread" benchmarks.

The `Html Preparation Code` section is empty, indicating that no HTML-specific code is being executed in this benchmark.

**Individual Test Cases**

There are two test cases:

1. **"unshift"`**
The benchmark definition logs the result of calling `itemsArray.unshift('olololol')`. The `unshift` method adds a new value to the beginning of an array.
2. **"spread"`**
The benchmark definition uses the spread operator (`...`) to create a new array by copying all elements from `itemsArray`. This creates a shallow copy of the original array.

**Options Compared**

In this benchmark, we have two options being compared:

1. **`unshift`**: Adds a value to the beginning of an array.
2. **`spread`**: Creates a shallow copy of an array using the spread operator.

**Pros and Cons of Each Approach**

**`unshift`**

Pros:

* Efficient for adding values to the beginning of an array, as it only needs to update the first element's index.
* Can be faster than other methods like `concat()` or creating a new array from scratch.

Cons:

* Modifies the original array. If you need to keep the original array unchanged, this might not be the best choice.
* May incur additional overhead if the array is large and needs to be reallocated.

**`spread`**

Pros:

* Creates a shallow copy of the original array, leaving it unchanged.
* Can be faster than other methods like `concat()` or using a loop to create a new array from scratch.

Cons:

* May incur additional overhead when creating a new array from scratch.
* If the array contains complex objects or references, this method may create multiple copies (not shallow copies), leading to increased memory usage and potential performance issues.

**Library/Features Used**

There is no explicit library used in these benchmark definitions. However, JavaScript's built-in `unshift()` and spread operator (`...`) are utilized.

No special JavaScript features or syntax are required for this benchmark.

**Other Alternatives**

For creating shallow copies of arrays, you can also use the following methods:

1. **`Array.prototype.slice()```**: Creates a shallow copy by returning a new array referencing elements from the original array.
2. **`Array.prototype.concat()````**: Creates a new array and returns it, copying all elements from the original array.

In summary, this benchmark compares the performance of two simple JavaScript methods: `unshift()` for adding values to an array's beginning and using the spread operator (`...`) for creating a shallow copy of an array. The choice between these approaches depends on your specific use case and requirements.

Related benchmarks:

unshift vs clone array (version: 0)

Comparing performance of: unshift vs spread

Created: 5 years ago by: Guest

Jump to the latest result

unshift

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):