Benchmark: unshift vs push array

Script Preparation code:

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

Tests:

unshift
console.log('unshift ', itemsArray.unshift('olololol'))
push
console.log('push ', itemsArray.push('olololol'))

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
unshift
push

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36

Browser/OS: Chrome 122 on Linux

View result in a separate tab

Test name	Executions per second
unshift	8882.9 Ops/sec
push	239190.1 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to help you understand what's being tested in the provided benchmark.

**Overview**

The benchmark compares the performance of two methods for adding an element to the end of an array in JavaScript: `unshift()` and `push()`. The test case is designed to measure which method is faster on a specific hardware configuration, in this case, Chrome 122 on a Linux desktop.

**Benchmark Definition JSON**

The benchmark definition JSON contains the following information:

* `Name`: The name of the benchmark, which is "unshift vs push array".
* `Script Preparation Code`: A JavaScript code snippet that creates an empty array `itemsArray` and populates it with 100,000 elements using a `for` loop. This code is executed before each test case to ensure consistent results.
* `Html Preparation Code`: An empty string, indicating no HTML preparation is required.

**Test Cases**

The benchmark consists of two individual test cases:

1. **unshift**: Measures the performance of calling `unshift()` on the `itemsArray` with the string "olololol".
2. **push**: Measures the performance of calling `push()` on the `itemsArray` with the string "olololol".

**Options Compared**

The two options being compared are:

* `unshift()`: Adds an element to the beginning of the array.
* `push()`: Adds an element to the end of the array.

**Pros and Cons**

* **Pros of using unshift():**
	+ Can be faster for arrays that need to maintain a specific order (e.g., sorting).
	+ Can reduce memory fragmentation by adding elements to the beginning of the array.
* **Cons of using unshift():**
	+ Can lead to slower performance when inserting or removing elements from the middle or end of the array, as it requires shifting all subsequent elements.
	+ May increase memory usage due to the need to allocate new memory for the added element at the beginning of the array.
* **Pros of using push():**
	+ Is generally faster and more efficient than `unshift()` when inserting or removing elements from the middle or end of the array, as it only requires updating a single index.
	+ Reduces memory fragmentation by allocating new memory for each added element at the end of the array.
* **Cons of using push():**
	+ May lead to slower performance when adding an element to the beginning of the array (i.e., `unshift()`).
	+ Can increase memory usage due to the allocation of new memory for each added element.

**Library**

There is no library mentioned in the benchmark definition, but it's likely that the `Array.prototype` methods (`unshift()` and `push()`) are being used.

**Special JS Feature or Syntax**

None are explicitly mentioned, but note that JavaScript has some features like `let`, `const`, and arrow functions (e.g., `() => { ... }`) that can affect performance. However, these are not relevant to this specific benchmark.

**Alternatives**

Other alternatives for adding elements to the end of an array in JavaScript include:

* Using `Array.prototype.concat()` or other methods that create a new array.
* Using `splice()` with the `-1` index (which inserts at the end).
* Implementing a custom solution using loops and indexing.

Keep in mind that these alternatives may have different performance characteristics and use cases, depending on the specific requirements of your application.

Related benchmarks:

unshift vs push array (version: 0)

Comparing performance of: unshift vs push

Created: 5 years ago by: Guest

Jump to the latest result

unshift

push

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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