Benchmark: unshift vs sort - MeasureThat.net

Script Preparation code:

var arr = [...Array(10000)].map((_,i) => i)

Tests:

unshift
arr.forEach((v,i) => { console.log(v,i); arr.unshift(arr.splice(i,1).shift()) })
swapping
arr.sort((a,b) => (a === b) ? 0 : (a < b) ? 1 : -1)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
unshift
swapping

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/134.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 134 on Android

View result in a separate tab

Test name	Executions per second
unshift	6.4 Ops/sec
swapping	5666.4 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.

**Benchmark Overview**

The benchmark is comparing two approaches: `unshift` and `sort`. The goal is to measure their performance, specifically how many times each operation can be executed per second on a given system configuration.

**Script Preparation Code**

The script preparation code generates an array of 10,000 random numbers using the spread operator (`Array(10000)`) and the `map()` function. This creates an array that can be modified by the test cases.

**Benchmark Definition Json**

The benchmark definition json contains two individual test cases:

1. **unshift**: This test case uses the `forEach` loop to iterate over the array, logging each element and its index. Inside the loop, it calls `arr.unshift(arr.splice(i, 1).shift())`, which performs an unshift operation on the array.
2. **swapping** (Note: The name of this test case is misleading, as it's not actually swapping elements. Instead, it's sorting the array).

**Library and Special JS Feature**

The `splice()` function used in the `unshift` test case is a built-in JavaScript method that modifies the original array by removing elements from their current positions. The `.shift()` method is also a built-in method that removes and returns the first element of an array.

**Options Compared**

Two options are being compared:

1. **unshift**: This approach inserts an element at the beginning of the array using `arr.unshift()`.
2. **sort**: This approach sorts the array in-place using the `sort()` method, which rearranges the elements based on a compare function (in this case, a simple equality check).

**Pros and Cons**

Here's a brief summary of the pros and cons of each approach:

* **unshift**:
	+ Pros: Can be faster for inserting an element at the beginning of the array.
	+ Cons: Requires modifying the original array by removing elements from their current positions, which can lead to unnecessary work if the array is large.
* **sort**:
	+ Pros: Can be more efficient for sorting a large array in-place, as it avoids creating new arrays or modifying the original array unnecessarily.
	+ Cons: May require more CPU cycles and memory for larger arrays, especially if the compare function is complex.

**Other Considerations**

When evaluating the performance of these two approaches, consider the following factors:

* **Array size**: Larger arrays may benefit from `sort` due to its in-place sorting capabilities.
* **Comparison function complexity**: If the comparison function is complex, it may slow down both `unshift` and `sort`.
* **System configuration**: The performance difference between `unshift` and `sort` may vary depending on the system's architecture, compiler optimizations, and available memory.

**Alternatives**

If you need to benchmark other approaches for inserting or sorting elements in an array, consider exploring these alternatives:

* **Array.prototype.at()** (ES6+): An alternative to `unshift`, which inserts an element at a specific index.
* **Array.prototype.insert()** (Proposed standardization): A proposed method for inserting an element at a specific index, currently not supported by all browsers or implementations.
* **Array.prototype.slice() + concat()**: One approach for sorting an array is to use `slice()` to extract the elements you want to keep and then concatenate them with another array created using `concat()`.

Related benchmarks:

unshift vs sort (version: 0)

Comparing performance of: unshift vs swapping

Created: 6 years ago by: Guest

Jump to the latest result

unshift

swapping

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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