Benchmark: Regex vs Index vs StartsWith

Script Preparation code:

var textAmount = 10000
var possibleLetters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789 ';
var getRandomLetter = function () {
  return Math.floor(Math.random() * possibleLetters.length);
};
var getRandomString = function (length) {
  let randomString = '';
  for (let i = 0; i < length; i++) {
    randomString += possibleLetters[getRandomLetter()];
  }
  return randomString;
};

var finalString = getRandomString(1000);

Tests:

Regex
for (let i = 0; i < textAmount; i++) { const string = getRandomString(1000); const regexStart = new RegExp(/^a/); regexStart.test(string); }
startsWith
for (let i = 0; i < textAmount; i++) { const string = getRandomString(1000); string.startsWith('a'); }
Index0
for (let i = 0; i < textAmount; i++) { const string = getRandomString(1000); string[0] === 'a'; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Regex
startsWith
Index0

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Overview**

The benchmark tests three different approaches to check if a string starts with a specific character or substring: regular expressions (`regex`), indexing (`Index0`), and the `startsWith` method. The goal is to determine which approach is the fastest.

**Options Compared**

1. **Regular Expressions (Regex)**:
	* Pros: Can be used to match more complex patterns, flexible, and widely supported.
	* Cons: Can be slower than other approaches for simple string checks, may have overhead due to compiling the regex pattern, and can be vulnerable to denial-of-service attacks if not properly configured.
2. **Indexing (Index0)**:
	* Pros: Can be faster than regular expressions for simple string checks, uses less memory, and is generally more efficient for small strings.
	* Cons: Limited to checking the first character of a string, may not work well with non-ASCII characters or special cases.
3. **startsWith Method**:
	* Pros: Fast, simple, and widely supported, making it a good choice for general-purpose string checks.
	* Cons: May not be as flexible as regular expressions, can have performance issues if used excessively.

**Library Used**

In this benchmark, the `RegExp` object is used to create a regex pattern. The `RegExp` constructor takes two arguments: the pattern and a flag indicating how to interpret the pattern. In this case, the pattern is `/^a/`, which matches any string that starts with the character 'a'.

**Special JavaScript Feature**

There is no special JavaScript feature or syntax used in this benchmark.

**Benchmark Preparation Code Explanation**

The script preparation code generates a large random string (`textAmount`) and defines two helper functions: `getRandomLetter` to generate a random letter, and `getRandomString` to generate a random string of a specified length. The final string is generated by concatenating random letters.

The benchmark definition scripts (Regex, Index0, and StartsWith) use the same approach to test each respective method. They loop `textAmount` times, generating a random string, creating an instance of the corresponding method (regex, indexing, or startsWith), and calling it with the generated string.

**Alternative Approaches**

Other approaches to check if a string starts with a specific character or substring could include:

1. Using a simple ASCII table to check if the first character matches.
2. Using a lookup table or an array to store common prefixes and check if the input string matches any of them.
3. Using a more advanced regular expression pattern that takes into account special characters, case sensitivity, and other factors.

Keep in mind that these alternative approaches might have different performance characteristics and may not be as widely supported as the approaches tested in this benchmark.

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/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36

Browser/OS: Chrome 107 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Regex	0.4 Ops/sec
startsWith	0.4 Ops/sec
Index0	0.4 Ops/sec

Related benchmarks:

Regex vs Index vs StartsWith (version: 0)

Comparing performance of: Regex vs startsWith vs Index0

Created: one year ago by: Guest

Jump to the latest result

Regex

startsWith

Index0

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):