Benchmark: arr unshift vs push + reverse (small array)

Script Preparation code:

var arr = [10];

Tests:

unshift
for (let i = 0; i < 10; i++){ arr.unshift(i); }
push + reverse
for (let i = 0; i < 10; i++){ arr.push(i); } arr.reverse();

Historical Performance Data aggregated from 94 community runs

Desktop Results:

Chrome 63 runs

unshift

2K/s

push + reverse

2K/s

Fastest: unshift (1.4x faster)

View exact numbers

✓ unshift: 2,391 ops/sec
• push + reverse: 1,662 ops/sec

Firefox 21 runs

unshift

60K/s

push + reverse

140/s

Fastest: unshift (428.0x faster)

View exact numbers

✓ unshift: 59,773 ops/sec
• push + reverse: 140 ops/sec

Safari 5 runs

unshift

281K/s

push + reverse

19/s

Fastest: unshift (15131.9x faster)

View exact numbers

✓ unshift: 280,592 ops/sec
• push + reverse: 19 ops/sec

Mobile Results:

Chrome 5 runs

unshift

2K/s

push + reverse

2K/s

View exact numbers

✓ unshift: 2,202 ops/sec
• push + reverse: 2,090 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

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: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36

Browser/OS: Chrome 138 on Windows

View result in a separate tab

push + reverse

1K/s

unshift

813/s

View exact numbers

Test name	Executions per second
✓ push + reverse	1,416 Ops/sec
unshift	813 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 benchmark and explain what's being tested, compared, and their pros and cons.

**Benchmark Overview**

The benchmark is comparing two approaches to add an element to an array:

1. `unshift`: Adding an element to the beginning of the array using the `unshift` method.
2. `push + reverse`: Adding an element to the end of the array using the `push` method, followed by reversing the entire array.

**Library Used**

The benchmark doesn't explicitly mention any libraries being used beyond JavaScript's built-in functionality. However, it's likely that the browser's implementation of JavaScript is using a specific library or engine that might affect the results.

**Special JS Features or Syntax**

There are no special JavaScript features or syntaxes mentioned in this benchmark. The focus is on comparing two common array manipulation techniques.

**Options Compared**

The benchmark is comparing the performance of:

1. `unshift`: Adding an element to the beginning of the array.
2. `push + reverse`: Adding an element to the end of the array and then reversing the entire array.

**Pros and Cons of Each Approach**

* `unshift`:
	+ Pros: Can be faster for small arrays, as it only needs to shift elements to make room for the new element.
	+ Cons: Can be slower for large arrays, as it requires shifting all elements down, which can lead to more memory accesses and updates.
* `push + reverse`:
	+ Pros: Suitable for larger arrays, as it avoids the need to shift elements down.
	+ Cons: Slower than `unshift` because of the additional step of reversing the entire array.

**Other Considerations**

* The benchmark is using a small array (only 10 elements) which might not accurately represent real-world scenarios. Larger arrays would likely favor `push + reverse`.
* The use of `let i = 0;` for looping instead of traditional `for` loops might add additional overhead due to the need to create and initialize local scope variables.
* The benchmark doesn't account for any potential optimizations or caching that the browser's JavaScript engine might perform.

**Alternatives**

If you wanted to explore other array manipulation techniques, here are a few alternatives:

1. `splice`: Removing and replacing elements at specific indices.
2. `concat`: Adding one or more arrays together using concatenation.
3. `slice` with `push` (or vice versa): Using `slice` to create a new array from a subset of the original array, then pushing the elements onto the end.

These alternatives might offer different performance characteristics depending on the specific use case and array size.

arr unshift vs push + reverse (small array) (version: 0)

Comparing performance of: `unshift vs push + reverse`

Created: 5 years ago by: Guest

Go to the latest result

unshift

push + reverse

Historical Performance Data aggregated from 94 community runs

Desktop Results:

Chrome 63 runs

Firefox 21 runs

Safari 5 runs

Mobile Results:

Chrome 5 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

arr unshift vs push + reverse (small array) (version: 0)

Comparing performance of: unshift vs push + reverse

Created: 5 years ago by: Guest

Go to the latest result

unshift

push + reverse

Historical Performance Data aggregated from 94 community runs

Desktop Results:

Chrome 63 runs

Firefox 21 runs

Safari 5 runs

Mobile Results:

Chrome 5 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `unshift vs push + reverse`