Benchmark: Regex vs startswith and slice single

Script Preparation code:

window.idregex = /^(?<type>shared)(?<id>.*)$/
window.str = 'shared:dfhalsdkfjhasldfiuyo324987';

Tests:

Regex
const match = str.match(idregex) const type = match?.groups.type; const id = match?.groups.id
starts with and slice
const type = 'shared'; str.startsWith(type) const id = str.slice('shared'.length)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Regex
starts with and slice

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark definition and test cases to explain what's being tested, compared, and their pros and cons.

**Benchmark Definition**

The JSON represents a JavaScript microbenchmark on MeasureThat.net. The benchmark compares two approaches: using regular expressions (`Regex`) and using the `startsWith` method with slicing (`startsWith and slice`).

**Script Preparation Code**

```javascript
window.idregex = /^(?<type>shared)(?<id>.*)$/\r\nwindow.str = 'shared:dfhalsdkfjhasldfiuyo324987';
```

This code defines a regular expression (`idregex`) that matches strings with a shared prefix (`shared` followed by some characters). It also sets up a test string (`str`) containing the same prefix.

**Html Preparation Code**

There is no HTML preparation code, which means this benchmark doesn't require any specific web page setup or initialization.

**Test Cases**

The individual test cases are:

1. **Regex**
```javascript
const match = str.match(idregex)
  const type = match?.groups.type;
  const id = match?.groups.id;
```
This test case uses the `match` method of the regular expression to extract the matched groups (`type` and `id`). The `?.groups` syntax is called "optional chaining" or "nullish coalescing," which allows safe navigation through potentially null values.

2. **startsWith and slice**
```javascript
const type = 'shared';
str.startsWith(type)
const id = str.slice('shared'.length)
```
This test case uses the `startsWith` method to check if the string starts with `'shared'`, and then uses slicing (`slice`) to extract the remaining characters.

**Comparisons**

The benchmark compares the performance of these two approaches:

* **Regex**: Uses regular expressions to match the string.
* **startsWith and slice**: Uses the `startsWith` method followed by slicing to extract the desired part of the string.

**Pros and Cons**

Here's a brief summary of each approach:

* **Regex**:
	+ Pros: Can be more flexible for complex matching, less code required.
	+ Cons: Performance can be slower due to regex engine overhead, may not work well with very large strings or complex patterns.
* **startsWith and slice**:
	+ Pros: Generally faster, as it avoids the overhead of a full regex match. Works well with short prefixes or suffixes.
	+ Cons: Requires more code for slicing and checking starts-with, which can lead to slightly longer execution times.

**Library and Special JS Features**

There's no explicit library mentioned in the benchmark definition. However, `optional chaining` (`.?.groups`) is a modern JavaScript feature introduced with ECMAScript 2020 (ES10). It allows safe navigation through potentially null values using the `.groups` property of the match object.

**Other Alternatives**

If you wanted to test alternative approaches, you could consider:

* Using other string matching methods, such as `indexOf` or `includes`.
* Implementing a custom regex engine or parser.
* Comparing performance with different JavaScript engines (e.g., V8, SpiderMonkey).

However, these alternatives might not be directly comparable to the `Regex` and `startsWith and slice` approaches in terms of simplicity, readability, and performance.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/115.0

Browser/OS: Firefox 115 on Windows

View result in a separate tab

Test name	Executions per second
Regex	4244426.5 Ops/sec
starts with and slice	126688216.0 Ops/sec

Related benchmarks:

Regex vs startswith and slice single (version: 0)

Comparing performance of: Regex vs starts with and slice

Created: one month ago by: Guest

Jump to the latest result

Regex

starts with and slice

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):