Benchmark: Array .push() vs .unshift()

Script Preparation code:

var arr = []

Tests:

.unshift()
arr.unshift(42)
.push()
arr.push(42)

Historical Performance Data aggregated from 51 community runs

Desktop Results:

Chrome 42 runs

.push()

11.9M/s

.unshift()

28K/s

Fastest: .push() (425.4x faster)

View exact numbers

✓ .push(): 11,872,798 ops/sec
• .unshift(): 27,911 ops/sec

Firefox 9 runs

.push()

29.9M/s

.unshift()

526K/s

Fastest: .push() (56.8x faster)

View exact numbers

✓ .push(): 29,870,250 ops/sec
• .unshift(): 525,825 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()

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 6 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:146.0) Gecko/20100101 Firefox/146.0

Browser/OS: Firefox 146 on Linux

View result in a separate tab

.push()

20.9M/s

.unshift()

657K/s

View exact numbers

Test name	Executions per second
✓ .push()	20,894,864 Ops/sec
.unshift()	656,856 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into explaining the benchmark and its components.

**What is tested:**

The provided JSON represents a JavaScript microbenchmark that compares the performance of two approaches: `arr.push()` and `arr.unshift()`. The test creates an empty array, `var arr = []`, and then pushes or unshifts a value (42) into it. The benchmark measures the time taken to execute these operations.

**Options compared:**

Two options are being compared:

1. **`arr.push(42)`**: This approach adds the value 42 to the end of the array using the `push()` method.
2. **`arr.unshift(42)`**: This approach inserts the value 42 at the beginning of the array using the `unshift()` method.

**Pros and cons:**

1. **`arr.push(42)`**:
	* Pros: More common and efficient way to add an element to the end of an array.
	* Cons: May require more memory allocations if the array is large, leading to slower performance due to garbage collection.
2. **`arr.unshift(42)`**:
	* Pros: Can be faster than `push()` for small arrays or when inserting at the beginning is necessary (e.g., sorting).
	* Cons: Requires more memory allocations and can lead to slower performance due to garbage collection, especially for large arrays.

**Library and purpose:**

The test uses no specific JavaScript library. It's a basic example of a microbenchmarking test that relies on the built-in JavaScript methods `push()` and `unshift()`.

**Special JS feature or syntax:**

There is no special JavaScript feature or syntax mentioned in this benchmark. The code only uses standard JavaScript constructs.

**Other alternatives:**

For benchmarking JavaScript performance, other approaches include:

1. **BenchmarkDotNet**: A popular benchmarking library for Node.js and browser environments.
2. **jsPerf**: A simple benchmarking tool that comes bundled with the Chromium codebase.
3. **Google Benchmark**: A high-performance benchmarking framework developed by Google.

When choosing a benchmarking approach, consider factors like ease of use, customization options, and compatibility with your target environment (e.g., Node.js, browser).

Array .push() vs .unshift() (version: 0)

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

Created: 9 years ago by: Guest

Go to the latest result

.unshift()

.push()

Historical Performance Data aggregated from 51 community runs

Desktop Results:

Chrome 42 runs

Firefox 9 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Array .push() vs .unshift() (version: 0)

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

Created: 9 years ago by: Guest

Go to the latest result

.unshift()

.push()

Historical Performance Data aggregated from 51 community runs

Desktop Results:

Chrome 42 runs

Firefox 9 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()`