Benchmark: Regex vs .startsWith 2

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:

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark and explain what's being tested, compared, and their pros/cons.

**Benchmark Overview**

The benchmark is designed to compare the performance of two string comparison methods: regular expressions (`regex`) and the `.startsWith()` method. The test creates a large dataset of random strings and iterates through it, performing either the regex or .startsWith() check on each string.

**Script Preparation Code**

The script preparation code sets up several variables:

* `window.regex`: a regular expression object (`/^test/`)
* `window.match`: a string literal ("test")
* `window.data`: an array of random strings (100,000 elements)
* `window.TOTAL_STRINGS`: the total number of strings in the dataset (100,000)

The script also defines two utility functions:

* `getRandomInt(max)`: generates a random integer between 0 and `max`
* `makeRandomString(len)`: generates a random string of length `len` using the `possible` character set

**Html Preparation Code**

The HTML preparation code is empty, which means no UI-related overhead is introduced during benchmarking.

**Individual Test Cases**

There are two test cases:

1. **Regex**: The script iterates through the dataset, applying the regex object (`/^test/`) to each string using `regex.test(str)`.
2. **.startsWith**: The script iterates through the dataset, checking if each string starts with the `match` string ("test") using `str.startsWith(match)`.

**Comparison**

The benchmark is comparing the performance of these two methods:

* **Regex (test)**: This method uses a regular expression to match the strings against the pattern (`/^test/`). The regex engine will attempt to find any substring that matches this pattern.
* **.startsWith**: This method uses the `startsWith()` method, which checks if the string starts with the specified value.

**Pros and Cons**

Here's a brief summary of each method:

### Regex (test)

Pros:

* Can match any substring, not just prefixes
* Can be used for more complex pattern matching

Cons:

* May be slower due to the complexity of regex evaluation
* More memory-intensive due to the regex engine's overhead

### .startsWith

Pros:

* Generally faster and more efficient than regex
* Less memory-intensive since it only checks for a prefix

Cons:

* Only matches strings that start with the specified value
* Limited to simple string comparisons

**Other Considerations**

In general, if you need to perform complex pattern matching or work with non-string data, regex might be a better choice. However, for simple string comparisons, .startsWith() is likely to be faster and more efficient.

Keep in mind that these results may vary depending on the specific use case and browser/OS combination.

**Alternative Approaches**

If you're looking for alternative methods, consider:

* **String.includes():** Similar to `.startsWith()`, but checks if the string includes any part of the specified value.
* **String.indexOf():** Finds the index of the first occurrence of the specified value in the string. This method can be slower than `.startsWith()` due to its search pattern.

Keep in mind that these alternatives might have different performance characteristics, so it's essential to test and benchmark them according to your specific requirements.

Related benchmarks:

Regex vs .startsWith 2 (version: 0)

Testing some things

Comparing performance of: Regex vs .startsWith

Created: 7 years ago by: Registered User

Jump to the latest result

Regex

.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):