Benchmark: findIndex (reversed) vs findIndex

Script Preparation code:

var arr = [];
var i = 0;

while (i <= 1E5) arr[i] = i++;

Tests:

findIndex reverse
const index = arr.length - arr.reverse().findIndex(item => item == 1E5) - 1;
findIndex
const index = arr.findIndex(item => item == 1E5);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
findIndex reverse
findIndex

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36

Browser/OS: Chrome 114 on Windows

View result in a separate tab

Test name	Executions per second
findIndex reverse	1019.6 Ops/sec
findIndex	5485165.5 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the explanation into smaller sections to help illustrate what's being tested and compared in this JavaScript microbenchmark.

**Benchmark Definition**

The benchmark is designed to compare two different approaches for finding the index of a specific element in an array:

1. `findIndex` with no reversal: This approach directly uses the `findIndex` method to find the index of the desired element without reversing the array.
2. `findIndex` after reversing and then iterating from the end: This approach first reverses the array, finds the index of the desired element using `findIndex`, and then subtracts 1 from the result to get the correct index.

**Options Compared**

The benchmark compares two different approaches:

* **Approach 1**: Using `findIndex` with no reversal.
	+ Pros: Simple and efficient. It leverages the built-in `findIndex` method, which is optimized for performance.
	+ Cons: May not be as efficient as other approaches if the array is very large or has a specific structure.
* **Approach 2**: Using `findIndex` after reversing and then iterating from the end.
	+ Pros: Can be more efficient in certain cases, especially when working with arrays of varying sizes. The reversal allows the algorithm to work in reverse order, which can reduce the number of iterations required.

**Library and Purpose**

Neither approach uses a specific library. Instead, it relies on built-in JavaScript methods:

* `findIndex`: A method that returns the index of the first element in an array that satisfies the provided testing function.
* `reverse()`: A method that reverses the order of elements in an array.

**Special JS Feature or Syntax**

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

**Other Considerations**

When choosing between these two approaches, consider the following factors:

* Array size: If you're working with very large arrays, Approach 1 (no reversal) might be more efficient due to reduced overhead from reversing the array.
* Array structure: If your array has a specific structure or is sorted in a particular way, Approach 2 (reversing and then iterating) might be more efficient.

**Alternatives**

Other alternatives for finding the index of an element in an array include:

* Using `indexOf()` instead of `findIndex()`, which returns -1 if no match is found.
* Implementing a custom search algorithm using loops or recursive functions.
* Utilizing libraries like Lodash or Ramda, which provide optimized implementations of common functional programming tasks.

These alternatives might be more suitable for specific use cases or performance-critical applications.

Related benchmarks:

findIndex (reversed) vs findIndex (version: 0)

Measuring which is faster

Comparing performance of: findIndex reverse vs findIndex

Created: one year ago by: Guest

Jump to the latest result

findIndex reverse

findIndex

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):