Benchmark: slice vs capturing group

Script Preparation code:

var IMAGE_SIZE_REGEX = /\/s\d{2,3}\//;
var IMAGE_SIZE_REGEX_GROUPS = /(.+)?\/s\d{2,3}\/(.+)?/;

function parseImageUrl(url) {
  const found = url.match(IMAGE_SIZE_REGEX);

  if (!found) {
    return null;
  }
  const { index } = found;
  const sizeStringLength = found[0].length;

  return {
    prefix: url.slice(0, index),
    suffix: url.slice(sizeStringLength + index),
  };
}

function parseImageGroups(url) {
  const found = url.match(IMAGE_SIZE_REGEX_GROUPS);

  if (!found) {
    return null;
  }

  return {
    prefix: found[1],
    suffix: found[2],
  };
}

Tests:

slice
parseImageUrl('prefix/s480/suffix');
groups
parseImageGroups('prefix/s480/suffix');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
groups

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/135.0.0.0 Safari/537.36

Browser/OS: Chrome 135 on Windows

View result in a separate tab

Test name	Executions per second
slice	9212910.0 Ops/sec
groups	4234999.0 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 its results to understand what's being tested.

**Benchmark Definition**

The benchmark is comparing two approaches: `slice` and `capturing group`. The script preparation code defines two regular expression patterns:

1. `IMAGE_SIZE_REGEX`: A simple pattern that matches a slash followed by one or three digits (`s\d{2,3}\//`). It captures the prefix of the URL before the size parameter.
2. `IMAGE_SIZE_REGEX_GROUPS`: An extended pattern that captures groups (optional) in the same format as the first pattern, but also includes an optional capture group for the suffix.

**Options being compared**

The two options being compared are:

1. `slice` : This approach uses the `slice()` method to extract the prefix and suffix from the URL. It's a simple and straightforward way to extract the desired parts of the URL.
2. `groups` : This approach uses the capturing groups in the regular expression pattern to extract the prefix and suffix. The idea is that by capturing the groups, you can avoid using `slice()` and potentially improve performance.

**Pros and Cons**

1. **slice()**:
	* Pros: Easy to understand and implement, widely supported.
	* Cons: May incur additional overhead due to the creation of a new string object, depending on the browser's string concatenation behavior.
2. **capturing groups (groups)**:
	* Pros: Can potentially avoid the overhead of creating new string objects, as it reuses existing character data in the regular expression pattern.
	* Cons: More complex and less intuitive than using `slice()`, requires understanding of regular expressions.

**Library and purpose**

The provided benchmark does not use any external libraries. However, some browsers' JavaScript engines (e.g., V8) have built-in support for regular expressions with capturing groups, which might be optimized to perform better in certain scenarios.

**Special JS feature or syntax**

This benchmark uses a special syntax for regular expressions called "capturing groups" (`(.+)?/s\d{2,3}/(.+)?`). This allows the pattern to capture parts of the string and include them as separate groups in the match result. The `?` after the first group makes it optional.

**Other considerations**

1. **Browser variability**: The benchmark's results may vary across different browsers due to differences in their JavaScript engines, string handling, and regular expression optimizations.
2. **Regular expression engine limitations**: Some browser's regular expression engines might have limitations or bugs that affect the performance of capturing groups.
3. **Code readability and maintainability**: While the `groups` approach might be more efficient, it can make the code harder to understand and maintain for developers without experience with regular expressions.

**Other alternatives**

If you're concerned about the performance impact of using `slice()`, you could consider other alternatives:

1. **Using a library like regex-performance**: This library provides optimized regular expression patterns and implementations that might be more efficient than the built-in engine.
2. **Rewriting the pattern**: You could try rewriting the pattern to avoid capturing groups or reduce the number of groups used.
3. **Using a different approach**: Depending on the specific requirements, you might consider using a different approach, such as parsing the URL as JSON or using a dedicated URL parsing library.

Keep in mind that the best approach will depend on your specific use case and performance requirements.

Related benchmarks:

slice vs capturing group (version: 0)

Comparing performance of: slice vs groups

Created: 4 years ago by: Guest

Jump to the latest result

slice

groups

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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