Benchmark: Move item in first place spread vs unshift

Script Preparation code:

var array = [1,2,3]
var index = 1;

Tests:

Unshift
array.unshift(array.splice(index, 1)[0]);
Spread
array = [ ...array.splice(index, 1), ...array];

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:

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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:**

The benchmark definition is a JSON object that defines two test cases:

1. `array.unshift(array.splice(index, 1)[0]);`
2. `array = [ ...array.splice(index, 1), ...array];`

Both tests aim to measure the performance of moving an item in the first place using different methods.

**Options Compared:**

The two options being compared are:

1. **Unshift**: This method uses the `unshift()` function to insert the removed element at the beginning of the array.
2. **Spread**: This method uses the spread operator (`...`) to create a new array with the removed element and then assigns it back to the original array using the assignment operator.

**Pros and Cons:**

**Unshift:**

Pros:

* This method is generally faster since it only requires a single operation (insertion at the beginning).
* It's more efficient for small arrays because it doesn't require creating a new array.

Cons:

* When dealing with large arrays, the performance difference between unshift and spread can be negligible due to the overhead of inserting an element at the beginning.
* Some versions of JavaScript may have issues with unshift() when dealing with very large arrays or sparse arrays (arrays with missing elements).

**Spread:**

Pros:

* This method is generally more efficient for large arrays because it allows the browser to reuse existing memory and avoid creating a new array.
* It's also more flexible since it can handle complex cases like inserting multiple elements at once.

Cons:

* This method requires creating a new array using the spread operator, which can be slower than unshift() for small arrays.
* The spread operator can lead to performance issues if not used correctly (e.g., when dealing with very large arrays).

**Library and Purpose:**

In this benchmark, no specific library is being used. However, it's worth noting that some libraries like Lodash or Ramda provide utility functions like `_.unshift()` or `R.unshift()` that can be used to implement the unshift() method.

**Special JS Features/Syntax:**

There are no special JavaScript features or syntax being tested in this benchmark. The code is straightforward and uses only standard JavaScript syntax.

**Other Alternatives:**

If you want to measure performance of moving an item in the first place, other alternatives could be:

* `array.splice(index, 1)[0] + array`: This method uses index shifting followed by element concatenation, which can lead to performance issues due to the overhead of creating a new string.
* `array.slice(0, index) + [array[index]] + array.slice(index + 1)`: This method uses slicing and concatenation to create a new array with the removed element.

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

Related benchmarks:

Move item in first place spread vs unshift (version: 0)

Move item in first place spread vs unshift

Comparing performance of: Unshift vs Spread

Created: 3 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):