Benchmark: startsWith vs regex 2

Script Preparation code:

var obj = {
  	__protot__: '__protot__',
	_prefixA: '_prefixA',
  	_prefixB: '_prefixB',
  	_prefixC: '_prefixC',
  	_prefixD: '_prefixD',
  	prefixA: '_prefixA',
  	prefixB: '_prefixB',
  	prefixC: '_prefixC',
  	prefixD: '_prefixD',
}

Tests:

startsWith
var count = 0 for (const key of Object.keys(obj)) { if (key.startsWith('__') || key.startsWith('_prefix')) count++ }
equals and startsWith
var count = 0 for (const key of Object.keys(obj)) { if (key === '__protot__' || key.startsWith('_prefix')) count++ }
regex
var count = 0 for (const key of Object.keys(obj)) { if (/^_(_|prefix)/.test(key)) count++ }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
startsWith
equals and startsWith
regex

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36

Browser/OS: Chrome 122 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
startsWith	4963087.5 Ops/sec
equals and startsWith	5404366.0 Ops/sec
regex	4355446.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is tested, compared, and other considerations.

**Benchmark Overview**

The benchmark compares three approaches to check if a key in an object starts with a specific prefix: `startsWith`, `equals and startsWith`, and regular expression (`regex`).

**Options Compared**

1. **startsWith**: Checks if the key starts with a specified prefix using the `startsWith()` method.
2. **equals and startsWith**: First checks if the key is equal to a specified value, then checks if it starts with another specified prefix using the `startsWith()` method. This approach is not optimized for performance as it performs two separate checks.
3. **regex**: Uses a regular expression (`/^_(_|prefix)/`) to match the key against the specified prefix.

**Pros and Cons**

1. **startsWith**:
	* Pros: Fast, concise, and widely supported.
	* Cons: May not work correctly with non-English characters or special keys (e.g., `__protot__`).
2. **equals and startsWith**:
	* Pros: None notable.
	* Cons: Inefficient, as it performs two separate checks. Not recommended for performance-critical applications.
3. **regex**:
	* Pros: Flexible and powerful, can match complex patterns.
	* Cons: Slower than `startsWith` due to the overhead of regular expression parsing and execution.

**Library/Functionality Used**

1. The benchmark uses JavaScript's built-in `Object.keys()` function to iterate over an object's keys.
2. The `startsWith()` method is used directly in two test cases (`equals and startsWith` and `regex`).

**Special JS Feature/Syntax**

None mentioned, but note that some older browsers may not support the `Object.keys()` function or `startsWith()` method.

**Other Alternatives**

1. For a more efficient alternative to `startsWith`, you could use a library like Lodash's `_.startsWith()` function.
2. If you need even greater flexibility with regular expressions, consider using a dedicated regex engine like RegExp.js.
3. In some cases, you might prefer to use a different approach, such as checking if the key is an exact match or using a prefix-based data structure (e.g., a trie).

Keep in mind that these alternatives may have their own trade-offs in terms of performance, complexity, and compatibility with older browsers or environments.

Related benchmarks:

startsWith vs regex 2 (version: 0)

Comparing performance of: startsWith vs equals and startsWith vs regex

Created: 2 years ago by: Registered User

Jump to the latest result

startsWith

equals and startsWith

regex

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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