Benchmark: arr unshift vs push + reverse (100 elements)

Script Preparation code:

var arr = [];

Tests:

unshift
for (let i = 0; i < 100; i++){ arr.unshift(i); }
push + reverse
for (let i = 0; i < 100; i++){ arr.push(i); } arr.reverse();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
unshift
push + reverse

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

Browser/OS: Chrome 119 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
unshift	390.8 Ops/sec
push + reverse	1563.3 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what is being tested, compared, and their pros and cons.

**Benchmark Definition**

The benchmark definition provides two test cases:

1. `arr unshift vs push + reverse (100 elements)`: This test compares the performance of two JavaScript methods on an array:
	* `unshift(i)`: adds an element to the beginning of the array.
	* `push(i)` followed by `reverse()`: adds an element to the end of the array and then reverses the order of the elements.

**Options Compared**

The benchmark is comparing the performance of two approaches:

1. **`unshift()`**: Adds an element to the beginning of the array. This method modifies the original array in-place, which can be more efficient than creating a new array.
2. **`push(i)` followed by `reverse()`**: Adds an element to the end of the array and then reverses the order of the elements. This approach creates two intermediate arrays (the original array with the added element and the reversed array), which can lead to increased memory usage.

**Pros and Cons**

1. **`unshift()`**:
	* Pros: In-place modification, potentially faster execution time since it doesn't require creating a new array.
	* Cons: May not be suitable for use cases where the original order of elements is important.
2. **`push(i)` followed by `reverse()`**:
	* Pros: Preserves the original order of elements and can be useful in certain scenarios, such as data processing pipelines.
	* Cons: Creates intermediate arrays, leading to increased memory usage and potentially slower execution time.

**Library Usage**

There is no library explicitly mentioned in the benchmark definition. However, it's worth noting that modern JavaScript engines like V8 (used by Chrome) optimize array operations, including `push()` and `reverse()`, which reduces the overhead of these methods.

**Special JS Feature/Syntax**

The benchmark does not use any special JavaScript features or syntax beyond standard language support.

**Other Considerations**

When evaluating this benchmark, consider the following:

* Memory usage: The `push(i)` followed by `reverse()` approach creates two intermediate arrays, which may lead to increased memory usage.
* Performance: The execution time of the `unshift()` method might be faster than the `push(i)` followed by `reverse()` approach due to in-place modification.

**Alternatives**

Other alternatives to consider when working with arrays include:

1. **`concat()`**: Creates a new array by concatenating two or more arrays.
2. **`splice()```**: Removes and replaces elements in an array while preserving the original order.
3. **`Array.prototype.set()` (ES2015+)**: Sets all elements of an array to a specified value.

Each approach has its use cases, and understanding their trade-offs is essential when working with arrays in JavaScript.

Related benchmarks:

arr unshift vs push + reverse (100 elements) (version: 0)

Comparing performance of: unshift vs push + reverse

Created: 2 years ago by: Guest

Jump to the latest result

unshift

push + reverse

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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