Benchmark: Matching regex with i flag vs lowercasing the string

Script Preparation code:

var str = "This is a Simple test!";
var simpleNeedle = new RegExp(/simple/);
var needleWithI = new RegExp(/simple/i);

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
lowercasing the string
RegExp + i

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	9888844.0 Ops/sec
RegExp + i	10379854.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in this benchmark.

The test is comparing two approaches:

1. **Lowercasing the string**: In this approach, the input string `str` is converted to lowercase using the `toLowerCase()` method before being passed to the regular expression `simpleNeedle`.
2. **RegExp with i flag**: In this approach, the same input string `str` is passed directly to the regular expression `needleWithI`, which has an `i` flag (case-insensitive) enabled.

**Pros and Cons:**

* Lowercasing the string:
	+ Pros: This approach can be more predictable and consistent, as the string is converted to a standard case before being compared. This can help avoid false positives or negatives due to differences in case.
	+ Cons: This approach may introduce additional overhead due to the string conversion step.
* RegExp with i flag:
	+ Pros: This approach allows for more flexibility and accuracy, as the regular expression can match strings regardless of case. This can be beneficial when dealing with ambiguous or variable-case input data.
	+ Cons: This approach may lead to false positives or negatives if the input string contains unexpected characters or edge cases.

**Library and purpose:**

The `RegExp` object is a built-in JavaScript library that provides support for regular expressions. In this benchmark, two different regular expressions are created:

* `simpleNeedle`: A non-casenormalized regular expression that matches only lowercase occurrences of the string "simple".
* `needleWithI`: A casenormalized regular expression with an `i` flag (case-insensitive) enabled, which can match both uppercase and lowercase occurrences of the string "simple".

**Special JS feature or syntax:**

In this benchmark, no special JavaScript features or syntax are used beyond what's standard in JavaScript.

**Other alternatives:**

One alternative approach could be to use a different string comparison method, such as using a custom case-insensitive matching algorithm. However, in general, regular expressions are well-suited for string matching tasks due to their flexibility and power.

Another alternative could be to test the performance of other string processing methods, such as using `String.prototype.localeCompare()` or `String.prototype.indexOf()`. However, these approaches may not offer significant improvements over the existing benchmark results.

Related benchmarks:

Matching regex with i flag vs lowercasing the string (version: 0)

Comparing performance of: lowercasing the string vs RegExp + i

Created: one year ago by: Guest

Jump to the latest result

lowercasing the string

RegExp + i

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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