Benchmark: Regex vs .startsWith

HTML Preparation code:

<div></div>

Script Preparation code:

window.regex = /^test/;
window.match = 'test';
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
var x = 0; var TOTAL_STRINGS = window.TOTAL_STRINGS; var data = window.data; var regex = window.regex; 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); x += 1; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Regex
.startsWith

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/105.0.0.0 Safari/537.36

Browser/OS: Chrome 105 on Linux

View result in a separate tab

Test name	Executions per second
Regex	92.6 Ops/sec
.startsWith	254.8 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark and its components.

**Benchmark Overview**

The MeasureThat.net website allows users to create and run JavaScript microbenchmarks. The provided benchmark is designed to compare the performance of two approaches: regular expression matching (`Regex`) and string prefix checking using the `startsWith` method (`.startsWith`).

**Script Preparation Code**

The script preparation code sets up the environment for the benchmark:

* It defines a regex pattern (`window.regex = /^test/;`) that matches the string "test".
* It initializes an array of strings (`window.data`) containing 100,000 random strings generated from the alphabet.
* It sets up variables for the total number of strings and executes per second.

**Html Preparation Code**

The HTML preparation code is empty, which means it doesn't add any additional overhead or complexity to the benchmark.

**Individual Test Cases**

There are two test cases:

1. **Regex**: This test case uses regular expression matching (`regex.test(str)`) to search for "test" in each string of the `data` array.
2. **.startsWith**: This test case uses the `startsWith` method to check if each string of the `data` array starts with "test".

**Library: None**

There are no external libraries used in this benchmark.

**Special JS Feature/Syntax: None**

Neither of the two approaches requires any special JavaScript features or syntax beyond regular expression matching and the `startsWith` method.

**Other Alternatives**

For a more comprehensive understanding, here are some alternative approaches that could be compared:

* **String.indexOf**: Another string searching method that can be used instead of `regex.test`.
* **String.includes**: A newer string searching method that is similar to `startsWith` but may have different performance characteristics.
* **Regular Expression Alternatives**: Other regular expression patterns, such as `window.regex = /test/;`, which might have slightly different performance characteristics.

In summary, this benchmark compares the performance of two simple string matching approaches: regular expression matching (`Regex`) and string prefix checking using the `startsWith` method (`.startsWith`). The results can provide insights into the performance characteristics of these approaches in JavaScript.

Related benchmarks:

Regex vs .startsWith (version: 0)

Testing some things

Comparing performance of: Regex vs .startsWith

Created: 5 years ago by: Guest

Jump to the latest result

Regex

.startsWith

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):