Benchmark: Matching regex with i flag vs lowercasing the string 2

Script Preparation code:

var str = "What if it's a much longer text here? Should we have an escape hatch? This is a Username!";
var strLower = str.toLowerCase();
var simpleNeedle = new RegExp('(user|account|log(i|o)n|net)((.)?(name|i.?d.?|log(i|o)n).?)?(.?((or|/).+|\\*|:))?$|benutzername|nome.?utente|nome (dell\')?account');
var needleWithI = new RegExp('(user|account|log(i|o)n|net)((.)?(name|i.?d.?|log(i|o)n).?)?(.?((or|/).+|\\*|:))?$|benutzername|nome.?utente|nome (dell\')?account', 'i');

Tests:

lowercasing the string
simpleNeedle.test(str.toLowerCase())
RegExp + i
needleWithI.test(str)
Already lowercased
simpleNeedle.test(strLower)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
lowercasing the string
RegExp + i
Already lowercased

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.6 Safari/605.1.15

Browser/OS: Safari 16 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
lowercasing the string	10122319.0 Ops/sec
RegExp + i	14076301.0 Ops/sec
Already lowercased	12466602.0 Ops/sec

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 JSON and explain what is being tested.

**Benchmark Definition:**

The benchmark definition represents three test cases for matching regular expressions with different approaches:

1. `simpleNeedle.test(strLower)`: This test case compares the performance of using a simple regular expression (`simpleNeedle`) on a pre-lowercased string (`strLower`).
2. `needleWithI.test(str)` : This test case compares the performance of using a regular expression with the `i` flag (`needleWithI`) on an unlowercased string (`str`).
3. `simpleNeedle.test(str)` : This test case is essentially the same as the first one, comparing the performance of using a simple regular expression on an unlowercased string (`str`).

**Options Compared:**

The benchmark compares three different approaches:

1. **Simple Regular Expression (without flags)**: The `simpleNeedle` regular expression is used without any flags.
2. **Regular Expression with `i` Flag**: The `needleWithI` regular expression is used with the `i` flag, which makes the pattern case-insensitive.

**Pros and Cons of Each Approach:**

1. **Simple Regular Expression (without flags)**:
	* Pros:
		+ Fastest approach
		+ Simple to implement
	* Cons:
		+ May not work correctly for case-insensitive matching
2. **Regular Expression with `i` Flag**:
	* Pros:
		+ Works correctly for case-insensitive matching
	* Cons:
		+ Slower than the simple approach due to the added overhead of flags

**Library Used:**

The benchmark uses the built-in JavaScript `RegExp` object, which is a part of the ECMAScript standard.

**Special JS Feature or Syntax:**

None mentioned in this specific benchmark. However, it's worth noting that the use of the `i` flag and case-insensitive matching might require support for Unicode normalization and case folding.

**Other Considerations:**

1. **String Preprocessing:** The benchmark uses string preprocessing to lowercase the input string (`strLower`) before testing with the simple regular expression.
2. **Regular Expression Optimizations:** It's worth noting that some modern JavaScript engines, like SpiderMonkey (used by Firefox) and V8 (used by Chrome), have optimized regular expressions for case-insensitive matching.

**Alternatives:**

If you wanted to benchmark different approaches or libraries, you could consider:

1. Using a different regular expression library or implementation, such as `regex-js` or `fast-regex`.
2. Comparing the performance of different string preprocessing techniques, such as using `toLowerCase()` vs. other normalization methods.
3. Testing case-insensitive matching with different flags, such as the `u` flag for Unicode normalization.

Keep in mind that benchmarking is all about isolating specific workloads and optimizing them for your use case. The specific approaches and libraries you choose will depend on your requirements and performance characteristics.

Related benchmarks:

Matching regex with i flag vs lowercasing the string 2 (version: 2)

Comparing performance of: lowercasing the string vs RegExp + i vs Already lowercased

Created: one year ago by: Registered User

Jump to the latest result

lowercasing the string

RegExp + i

Already lowercased

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):