Benchmark: Finding duplicates

HTML Preparation code:

<script src='https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js'></script>

Script Preparation code:

var max = 5000;

var arr = [];
for (let i = 0; i < max; i++) {
  arr.push({ value: i});
  // create an occasional duplicate
  if (i % 10 === 0) {
    arr.push({ value: i});
  }
}

Tests:

Filter
var duplicates = arr.filter((item, _, items) => items.find(dupItem => dupItem.value === item.value));
Group by
var grouped = _.groupBy(arr, item => item.value); var duplicates1 = _.flatten(_.filter(grouped, group => group.length > 1));

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Filter
Group by

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided JSON data and explain what's being tested.

**Benchmark Definition**

The benchmark definition is a JavaScript script that creates an array `arr` of 5000 objects, where each object has a unique value between 0 and 4999. Every 10th iteration, another duplicate object with the same value is added to the array.

The script preparation code is executed before running the benchmark, and it sets up the initial conditions for the benchmark.

**Html Preparation Code**

The HTML preparation code includes a link to a CDN (Content Delivery Network) hosted version of the Lodash library, which provides various utility functions. In this case, the `lodash.min.js` file is included.

**Individual Test Cases**

There are two individual test cases:

1. **Filter**

This test case uses the built-in JavaScript `filter()` method to find duplicates in the array. The filter function takes an item from the array and checks if any other item has the same value as this item using a closure. However, it seems that there's a bug in this implementation because the callback function is missing its first argument (the current item) and its second argument (the index of the current item).

The actual implementation should be `arr.filter((item, index, array) => { ... });`.

2. **Group by**

This test case uses the Lodash library to group the array by value and then filter out groups with a length greater than 1.

**Library: Lodash**

Lodash is a popular utility library for JavaScript that provides various functions for tasks like string manipulation, array manipulation, and more. In this case, `groupBy()` is used to group the array by value.

The `flatten()` function is also used in conjunction with `filter()` to further process the grouped data.

**Special JS Feature/Syntax**

There's no special JavaScript feature or syntax being tested here. The code is standard JavaScript, and it doesn't utilize any advanced features like async/await, Promises, or modern JavaScript syntax.

**Other Alternatives**

If you wanted to implement this benchmark without using Lodash, you could achieve similar results by writing a custom function to group the array by value and filter out groups with a length greater than 1. Here's an example:
```javascript
function groupBy(arr, key) {
  const result = {};
  arr.forEach((item) => {
    if (!result[item[key]]) {
      result[item[key]] = [];
    }
    result[item[key]].push(item);
  });
  return Object.keys(result).map((key) => result[key]);
}

function findDuplicates(arr) {
  const grouped = groupBy(arr, 'value');
  return _.flatten(grouped.filter((group) => group.length > 1));
}
```
However, using a library like Lodash can simplify the code and make it more efficient, especially for larger datasets.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Linux; Android 10; SM-G9650) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.141 Mobile Safari/537.36

Browser/OS: Chrome Mobile 87 on Android

View result in a separate tab

Test name	Executions per second
Filter	19.0 Ops/sec
Group by	1115.9 Ops/sec

Related benchmarks:

Finding duplicates (version: 0)

Comparing performance of: Filter vs Group by

Created: 3 years ago by: Guest

Jump to the latest result

Filter

Group by

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):