Benchmark: .unshift() vs .push() + .reverse()

Script Preparation code:

window.ELE_PER_CYCLE = 100;

Tests:

.unshift()
const reps = window.ELE_PER_CYCLE; const arr = []; for (let i = 0; i < reps; ++i) { arr.unshift(i); }
.push() + reverse()
const reps = window.ELE_PER_CYCLE; const arr = []; for (let i = 0; i < reps; ++i) { arr.push(i); } arr.reverse();

Historical Performance Data aggregated from 8 community runs

Desktop Results:

Firefox 8 runs

.push() + reverse()

2.6M/s

.unshift()

287K/s

Fastest: .push() + reverse() (9.1x faster)

View exact numbers

✓ .push() + reverse(): 2,614,305 ops/sec
• .unshift(): 287,124 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: 9 days ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:155.0) Gecko/20100101 Firefox/155.0

Browser/OS: Firefox 155 on Linux

View result in a separate tab

.push() + reverse()

5.0M/s

.unshift()

396K/s

View exact numbers

Test name	Executions per second
✓ .push() + reverse()	4,953,966 Ops/sec
.unshift()	396,090 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 is being tested, the options compared, pros and cons of each approach, and other considerations.

**Benchmark Definition:**

The benchmark is designed to compare the performance of two JavaScript methods:

1. `.unshift()`
2. `.push()` followed by `.reverse()`

The benchmark is testing how many elements can be added to an array in a single cycle (defined by `window.ELE_PER_CYCLE = 100;`) using these two approaches.

**Options Compared:**

* `.unshift()`: adds an element to the beginning of an array
* `.push()` followed by `.reverse()`: adds an element to the end of an array and then reverses the order of the elements

**Pros and Cons of Each Approach:**

1. `.unshift()`:
	* Pros: can add an element to the beginning of the array, which might be beneficial for certain use cases (e.g., inserting new data at the start of a sorted array).
	* Cons: can be slower than `.push()` because it involves shifting all elements after the insertion point.
2. `.push()` followed by `.reverse()`:
	* Pros: can add an element to the end of the array efficiently, and then reversing the array only affects the last `n` elements (where `n` is the length of the array). This approach can be beneficial for performance-critical code that needs to reverse arrays frequently.
	* Cons: involves two separate operations (`push()` and `.reverse()`), which might incur additional overhead.

**Library:**

The benchmark uses no external libraries. The JavaScript code is executed in a browser environment, and the results are reported using a simple format (e.g., `ExecutionsPerSecond`).

**Special JS Feature/Syntax:**

There are no special JavaScript features or syntax mentioned in this benchmark. However, it's worth noting that some older browsers might not support modern JavaScript features like arrow functions, template literals, or let/catch blocks.

**Other Considerations:**

* The benchmark assumes a fixed number of cycles (`window.ELE_PER_CYCLE = 100;`) to determine the execution rate. This means that the results are sensitive to the specific value of `ELE_PER_CYCLE`.
* The benchmark only measures the performance of adding elements to the array, not the performance of any other operations (e.g., searching, indexing) on the same array.
* The results might vary depending on the specific use case and requirements. For example, if you need to frequently insert new data at the beginning of a sorted array, `.unshift()` might be a better choice.

**Alternatives:**

If you want to compare other JavaScript methods for adding elements to an array or reversing arrays, you could consider the following alternatives:

* Use other array manipulation methods like `concat()`, `splice()`, or `insertAt()`.
* Compare different sorting algorithms (e.g., bubble sort, quicksort, mergesort).
* Test the performance of different data structures (e.g., linked lists, stacks, queues).

.unshift() vs .push() + .reverse() (version: 0) Benchmark.js

Comparing performance of: `.unshift() vs .push() + reverse()`

Created: 4 years ago by: Guest

Go to the latest result

.unshift()

.push() + reverse()

Historical Performance Data aggregated from 8 community runs

Desktop Results:

Firefox 8 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

.unshift() vs .push() + .reverse() (version: 0) Benchmark.js

Comparing performance of: .unshift() vs .push() + reverse()

Created: 4 years ago by: Guest

Go to the latest result

.unshift()

.push() + reverse()

Historical Performance Data aggregated from 8 community runs

Desktop Results:

Firefox 8 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()`