Benchmark: contains vs regex

Script Preparation code:

var urls = `/as/
/a/b
/c/d
/e/f
`;
var url = 'http://example.com/a/b/cd/e/f';
var list = urls.match(/[^\r\n]+/g);
var regex = new RegExp(urls.match(/[^\r\n]+/g).join('|'));

Tests:

list
for(var i=0; i++; i<list.length) { if (url.contains(list[i])) { break; } }
regex
1+1

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
list
regex

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested, compared options, pros and cons, library usage, special JS features, and other considerations.

**Benchmark Description**

The benchmark measures the performance difference between two approaches: using `contains()` method on a string (`list[i]`) versus using regular expressions to match strings against a pattern (`regex`).

**Comparison Options**

1. **Using `contains()` method**: This approach uses the built-in `contains()` method of JavaScript strings, which is implemented in the browser's engine.
2. **Using Regular Expressions (Regex)**: This approach uses the `new RegExp()` constructor to create a regular expression pattern and then uses the `test()` method to match the string against this pattern.

**Pros and Cons**

* **Using `contains()` method**:
	+ Pros: Typically faster and more efficient, as it's implemented in the browser's engine.
	+ Cons: May not work correctly for all cases (e.g., edge cases like Unicode characters), especially if the input strings are very large or complex.
* **Using Regular Expressions (Regex)**:
	+ Pros: More flexible and powerful than `contains()`, with support for regular expression syntax features like character classes, quantifiers, and anchors. However, this can come at a performance cost.
	+ Cons: Slower and more resource-intensive due to the overhead of creating and executing regular expressions.

**Library Usage**

There is no explicit library mentioned in the benchmark definition or test cases. However, it's worth noting that ` RegExp` objects are part of the JavaScript Standard Library, which means they're implemented by the browser and don't require an additional library inclusion.

**Special JS Features**

* **String `contains()` method**: This method is not a standard part of JavaScript. It's likely that this benchmark tests the implementation of the `contains()` method in the specific browser being tested.
* **Regular Expressions (Regex)**: Regular expressions are a powerful feature in JavaScript, and their usage in this benchmark demonstrates the need for efficient execution.

**Other Considerations**

* The benchmark uses a fictional `urls` string to create a list of strings (`list`) that will be matched against a URL (`url`). This setup ensures consistent test inputs.
* The benchmark assumes that the input strings are encoded as UTF-8, which is the default encoding for JavaScript strings.

**Alternatives**

If you wanted to write similar benchmarks using other approaches, here are some alternatives:

1. **Using `indexOf()` method**: Instead of using the `contains()` method or regular expressions, you could use the `indexOf()` method to find the index of a substring within a string.
2. **Using a different regular expression syntax**: You could experiment with alternative regular expression syntax features, such as lookaheads or lookbehinds, to see how they impact performance.
3. **Testing with larger input datasets**: To further test the performance of these approaches, you could increase the size of the input dataset and observe how the results change.

Keep in mind that writing benchmarks requires a good understanding of the JavaScript engine's implementation details and the specific features being tested.

Latest run results:

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

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

Browser/OS: Firefox 109 on Windows

View result in a separate tab

Test name	Executions per second
list	817868032.0 Ops/sec
regex	882441152.0 Ops/sec

Related benchmarks:

contains vs regex (version: 0)

Comparing performance of: list vs regex

Created: 4 years ago by: Guest

Jump to the latest result

list

regex

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):