Benchmark: lastIndexOf vs split vs regex

Script Preparation code:

var str = 'player/attack-bottom/1'

Tests:

lastIndexOf
const idx = str.lastIndexOf('/') const r1 = str.substring(0, idx) const r2 = str.substring(idx + 1, str.length)
split
const splited = str.split('/') const r1 = splited[0] const r2 = splited[splited.length - 1]
regex
const splited = str.match(/[^\/]+/g) const r1 = splited[0] const r2 = splited[splited.length - 1]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
lastIndexOf
split
regex

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 benchmark and explain what's being tested, compared, and its pros and cons.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmarking test case on MeasureThat.net. The test is designed to compare the performance of three different approaches: `lastIndexOf`, `split`, and regular expressions (`regex`) for extracting a specific pattern from a string.

**Approaches Compared**

1. **`lastIndexOf`**: This method searches for the last occurrence of a specified value in a string and returns its index.
2. **`split`**: This method splits a string into an array of substrings based on a specified separator (in this case, the `/` character).
3. **`regex`** (regular expressions): This approach uses a pattern to match a specific sequence of characters in a string and extracts the matched substring.

**Pros and Cons**

1. **`lastIndexOf`**:
	* Pros: Simple, straightforward implementation, fast execution.
	* Cons: May not be suitable for all use cases (e.g., finding the last occurrence of a value that may not exist).
2. **`split`**:
	* Pros: Easy to implement, works well for simple string splitting tasks.
	* Cons: May not be efficient for large strings or complex splitting requirements.
3. **`regex`**:
	* Pros: Flexible, can match complex patterns, and is suitable for most use cases.
	* Cons: May have higher overhead due to the need to compile and execute a regular expression pattern.

**Library Usage**

None of the test cases explicitly use any JavaScript libraries besides the built-in `String` methods. However, if we were to consider the broader context of these methods, we could argue that `lastIndexOf`, `split`, and regular expressions are part of the standard JavaScript API.

**Special JS Feature or Syntax**

There is no specific special feature or syntax used in this benchmarking test case beyond what's required for each approach. The code snippets provided demonstrate basic string manipulation techniques.

**Other Alternatives**

If you're looking for alternative approaches to extract a pattern from a string, some other options include:

* Using `String.prototype.replace()` with a callback function.
* Utilizing `String.prototype.indexOf()` and manual handling of the match result.
* Leveraging a library like Lodash or Ramda for more complex string manipulation tasks.

In conclusion, this benchmarking test case provides a good representation of the performance differences between three common approaches to extracting patterns from strings in JavaScript.

Latest run results:

Run details: (Test run date: 2 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:129.0) Gecko/20100101 Firefox/129.0

Browser/OS: Firefox 129 on Windows

View result in a separate tab

Test name	Executions per second
lastIndexOf	2414932224.0 Ops/sec
split	14326296.0 Ops/sec
regex	6945606.5 Ops/sec

Related benchmarks:

lastIndexOf vs split vs regex (version: 0)

testing speed

Comparing performance of: lastIndexOf vs split vs regex

Created: 9 months ago by: Guest

Jump to the latest result

lastIndexOf

split

regex

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):