Benchmark: 2x JS Regex vs .startsWith

HTML Preparation code:

<div></div>

Script Preparation code:

window.regexStart = /^(test|test2)/;
window.regexEnd = /test$/;
window.match = 'test';
window.matchLength = window.match.length;
var data = window.data = [];
const possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
var TOTAL_STRINGS = window.TOTAL_STRINGS = 100000;

function getRandomInt(max) {
  return Math.floor(Math.random() * max);
}

function makeRandomString(len) {
  var text = "";
  for( var i=0; i < len; i++ ) {
    text += possible.charAt(getRandomInt(possible.length));
  }
  return text;
}

while (data.length < TOTAL_STRINGS) {
  data.push(makeRandomString(getRandomInt(20)));
}

Tests:

regex start
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var regex = window.regexStart; while (x < TOTAL_STRINGS) { const str = data[x]; regex.test(str); x += 1; }
startsWith
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var match = window.match; while (x < TOTAL_STRINGS) { const str = data[x]; str.startsWith(match) === 0; str.startsWith(match) === 0; x += 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
regex start
startsWith

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the provided benchmark and explain what's being tested.

**Overview**

The benchmark is designed to compare the performance of two JavaScript methods: regular expression (regex) matching (`window.regexStart`) and the `startsWith()` method. The test is repeated with 100,000 random strings generated from a large character set.

**What's being tested?**

* **Regex start**: This test case uses the regex `window.regexStart` to match each random string in the dataset. The goal is to determine how fast this approach can iterate through the entire dataset.
* **startsWith**: This test case uses the `startsWith()` method to check if each random string starts with a specific substring (`window.match`). The goal is to measure how quickly this approach can perform the same iteration.

**Options compared**

The benchmark compares two approaches:

1. **Regex start**: Uses a regex pattern to match strings.
2. **startsWith**: Uses the `startsWith()` method to check if strings start with a specified substring.

**Pros and cons of each approach:**

* **Regex start**:
	+ Pros:
		- Can be more flexible for complex matching requirements.
		- Can be optimized for performance using techniques like caching or memoization.
	+ Cons:
		- May have slower startup times due to regex compilation.
		- Can be affected by the complexity of the regex pattern, leading to slower performance.
* **startsWith**:
	+ Pros:
		- Faster startup times compared to regex start.
		- Can be optimized for performance using techniques like caching or memoization.
	+ Cons:
		- Less flexible than regex start for complex matching requirements.

**Library used**

In this benchmark, the `startsWith()` method is part of the JavaScript standard library. The `regexStart` variable is not a built-in function but rather a custom implementation provided in the script preparation code.

**Special JS feature or syntax**

None are mentioned specifically, except for the use of `RegExp` (regex) patterns and string methods like `startsWith()`. No special features or syntax beyond standard JavaScript are used in this benchmark.

**Other alternatives**

If you wanted to compare these approaches with alternative methods, here are some options:

* **Using a different regex engine**: Some browsers have built-in regex engines that can be faster than the JavaScript engine. You could test using a library like `regex-js` or `punycode`.
* **Using a different string comparison method**: Instead of `startsWith()`, you could use other methods like `localeCompare()` or `indexOf()`.
* **Using a different programming language**: You could rewrite the benchmark in a language with built-in support for regex patterns, like Python.

Keep in mind that these alternatives would change the nature of the benchmark and might not provide comparable results. The focus on JavaScript makes this benchmark particularly relevant to developers familiar with the language.

Related benchmarks:

2x JS Regex vs .startsWith (version: 0)

fork of https://www.measurethat.net/Benchmarks/Show/975/11/regex-vs-indexof-vs-startswith-vs-substr

Comparing performance of: regex start vs startsWith

Created: 4 years ago by: Guest

Jump to the latest result

regex start

startsWith

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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