Benchmark: regex vs length - MeasureThat.net

Script Preparation code:

regexp = new RegExp(/([0-9]+|.{2})/g)
lengthRegexp = new RegExp(/[^0-9]/g)
testString = '99ee'

Tests:

match
const matches = regexp.test(testString)
length
const matches = testString.replace(lengthRegexp, '').length || testString.length > 1

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
match
length

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON data to understand what is being tested in this JavaScript microbenchmark.

**Benchmark Overview**

The benchmark compares two approaches: using a regular expression (`regexp`) and calculating the length of a string minus the number of non-digit characters (`lengthRegexp`). The test cases are designed to measure the performance difference between these two methods for matching or replacing specific patterns in a string.

**Regular Expression Approach (regexp)**

* **Purpose**: Match any sequence of one or more digits (`[0-9]+`) followed by either a digit or at least two characters (`.{2}`) using a regular expression.
* **Library**: The `RegExp` constructor is used to create a new regular expression object, which provides various methods for searching and manipulating strings.
* **Pros**:
	+ Flexible pattern matching with support for complex character classes and quantifiers.
	+ Can be optimized using flags (e.g., `g` for global search) to improve performance.
* **Cons**:
	+ Can be slower than simple string length calculations due to the overhead of regular expression engine.
	+ May incur additional memory usage compared to a simple string manipulation.

**Length Calculation Approach**

* **Purpose**: Calculate the difference in string lengths between two substrings: one containing only non-digit characters (`[^0-9]`) and the other being the original string minus these non-digit characters.
* **Pros**:
	+ Simple, lightweight, and fast, as it only requires basic arithmetic operations.
	+ Can be optimized using caching or memoization techniques to improve performance.
* **Cons**:
	+ May not be suitable for complex pattern matching scenarios due to its simplicity.

**Other Considerations**

* The test string `testString = '99ee'` is used consistently across both test cases, ensuring that the results are comparable. However, it's worth noting that this string may contain more than just non-digit characters (e.g., letters), which might affect the performance difference between the two approaches.
* The use of flags like `g` in the regular expression can significantly impact performance, but it's not mentioned in the provided JSON data.

**Alternatives**

Other alternatives for benchmarking JavaScript string manipulation could include:

1. Simple substring extraction using slicing (`testString.slice(0, 3)`) or indexing (`testString[0]`).
2. Using a library like `lodash` which provides optimized string manipulation functions (e.g., `_.slice`, `_.indexOf`).
3. Comparing performance of JavaScript engines with built-in string manipulation functions (e.g., `String.prototype.indexOf`, `String.prototype.replace`) versus third-party libraries or custom implementations.

These alternatives would require additional setup and configuration to produce comparable results, but they might provide more accurate representations of real-world use cases or specific requirements.

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.117 Safari/537.36

Browser/OS: Chrome 79 on Windows

View result in a separate tab

Test name	Executions per second
match	1336503.5 Ops/sec
length	1020148.1 Ops/sec

Related benchmarks:

regex vs length (version: 0)

Comparing performance of: match vs length

Created: 4 years ago by: Registered User

Jump to the latest result

match

length

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):