Benchmark: regex vs startWith

Script Preparation code:

var foo = ['+++', '---', '===', '@@@', null, undefined, '', 'foo'];
var test = [];

for (var i = 0; i < 1000; i++) {
  test = [...test, ...foo];
}

Tests:

regex
test.map((x) => /^\+\-\=\@/.test(x) ? "'" + x : x);
startWith
test.map((x) => { if ( x?.startsWith('+') || x?.startsWith('-') || x?.startsWith('=') || x?.startsWith('@') ) { return "'" + x; } return x; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
regex
startWith

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/119.0

Browser/OS: Firefox 119 on Ubuntu

View result in a separate tab

Test name	Executions per second
regex	6216.2 Ops/sec
startWith	7478.9 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the explanation of the provided benchmark.

**What is being tested?**

The benchmark measures the performance difference between two approaches to check if a string starts with a specific character or substring: regular expressions (`regex`) and the `startsWith` method (also known as "string matching" or "substring checking").

In this specific test, both methods are applied to an array of strings `foo`, which contains a mix of strings with different characters, including some null and undefined values. The benchmark is run 1000 times for each string in the array.

**Options compared**

The two options being compared are:

1. **Regular Expressions (`regex`)**: This approach uses a regular expression to check if a string starts with a specific character or substring. In this case, the regular expression `^\\+\\-\\=\\@/` matches any string that starts with one of these characters.
2. **`startsWith` method**: This is a built-in JavaScript method that checks if a string starts with a specified value.

**Pros and Cons**

Here's a brief summary of the pros and cons of each approach:

* **Regular Expressions (`regex`)**:
	+ Pros: Can be used to check for more complex patterns, can be more efficient than `startsWith` for certain use cases.
	+ Cons: Can be slower than `startsWith` for simple string matching, may have performance implications due to the overhead of compiling regular expressions.
* **`startsWith` method**:
	+ Pros: Faster and more lightweight than regular expressions, well-suited for simple string matching.
	+ Cons: May not be as flexible as regular expressions, can be slower for complex patterns.

**Library used**

In this benchmark, no external library is explicitly mentioned. However, the `test.map()` function is used to apply the testing logic to each element in the array `foo`. This suggests that the benchmark is using built-in JavaScript functionality.

**Special JS feature or syntax**

There's a subtle point worth mentioning: the use of the optional chaining operator (`?.`) in the `startsWith` method implementation. This operator is only available in ECMAScript 2020 and later versions of JavaScript. In earlier versions, you would need to use explicit null checks instead.

**Other alternatives**

If you wanted to test other approaches to string matching or substring checking, some possible alternatives could include:

* Using a different built-in method, such as `includes()` or `slice()`.
* Implementing a custom string matching algorithm using bitwise operations or arithmetic.
* Comparing the performance of a third-party library for regular expressions or string matching.

Related benchmarks:

regex vs startWith (version: 0)

Comparing performance of: regex vs startWith

Created: one year ago by: Guest

Jump to the latest result

regex

startWith

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):