Benchmark: Lodash "unionWith" "unionBy" corrected

HTML Preparation code:

<script src='https://cdn.jsdelivr.net/npm/lodash@4.17.10/lodash.min.js'></script>

Script Preparation code:

var users = [
  { 'name': 'barney',  'age': 36 },
  { 'name': 'pebbles', 'age': 5 }
];

var newUsers = [
  { 'name': 'fred',    'age': 40 },
  { 'name': 'barney',  'age': 36 },
  { 'name': 'pebbles', 'age': 2 }
];

for(let i = 0; i < 2000; i++) {
  var newUser = { 'name': 'user_' + i, 'age': Math.floor(Math.random() * i) };
  newUsers.push(newUser);
}

Tests:

unionWith
const unionUsers1 = _.unionWith(newUsers, users, (newUser, user) => newUser.name === user.name);
unionBy
const unionUsers2 = _.unionBy(newUsers, users, 'name');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
unionWith
unionBy

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmarking test cases on MeasureThat.net.

**Benchmark Overview**

The test measures performance differences between two methods of merging arrays of objects using Lodash, a popular JavaScript utility library. The two methods are:

1. `unionWith`
2. `unionBy`

**What is tested?**

* **`unionWith`**: This method merges two arrays of objects into a new array by comparing and matching the values in each object based on their keys (i.e., properties). It uses a custom comparison function to determine which key(s) to match.
* **`unionBy`**: This method also merges two arrays of objects into a new array, but it uses an existing property as a key for comparison. In this case, the `name` property is used.

**Options compared**

The benchmark compares the performance of these two methods:

Pros and Cons:

* **`unionWith`**:
	+ Pros: Provides more control over which keys to match, can be useful when dealing with complex objects.
	+ Cons: Requires a custom comparison function, can be slower due to additional overhead.
* **`unionBy`**:
	+ Pros: Easier to use, requires less code and configuration.
	+ Cons: Only compares by one property (`name`), may not work well for more complex data.

**Library and purpose**

Lodash is a JavaScript utility library that provides various functions for common tasks, including array manipulation (e.g., `unionWith`, `unionBy`). The specific versions used in the benchmark are:

* Lodash 4.17.10

The `lodash.min.js` file is included from a CDN to make it easily reproducible.

**Special JS features or syntax**

None mentioned.

**Other alternatives**

While not explicitly listed, alternative approaches to merging arrays of objects could include:

1. Using `concat()` and filtering ( manual implementation)
2. Using `Array.prototype.reduce()` with an accumulator
3. Using a custom iterative approach

However, these alternatives might be slower and less concise than using Lodash's built-in methods (`unionWith`, `unionBy`).

**Benchmark preparation code**

The provided script preparation code generates two arrays of objects (users) with random properties and values. It then creates a new array of objects to merge into, which is populated on the fly using an iterative approach.

Keep in mind that this code generation might not accurately represent real-world usage scenarios, as it's intended for benchmarking performance.

**Latest benchmark result**

The latest results show:

* `unionBy` outperforms `unionWith` by a significant margin (≈ 50 times faster).

These differences are likely due to the custom comparison function and potential overhead in `unionWith`. However, the actual performance impact may vary depending on the specific use case.

Latest run results:

Run details: (Test run date: 5 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36

Browser/OS: Chrome 123 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
unionWith	91.6 Ops/sec
unionBy	4604.0 Ops/sec

Related benchmarks:

Lodash "unionWith" "unionBy" corrected (version: 0)

Comparing performance of: unionWith vs unionBy

Created: 5 months ago by: Guest

Jump to the latest result

unionWith

unionBy

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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