Benchmark: JS regexp - MeasureThat.net

Script Preparation code:

var url = '/c/category/some-stuff.html';
var regex = /^(\/nxp|\/_next\/static|\/_next\/image|\/favicon.ico)/;

Tests:

RegExp.text
if (!regex.test(url)) console.log('passed');
StartsWith.text
if (!url.startsWith('/nxp') && !url.startsWith('/_next/static') && !url.startsWith('/_next/image') && !url.startsWith('/favicon.ico')) console.log('passed');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
RegExp.text
StartsWith.text

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36 OPR/87.0.0.0

Browser/OS: Opera 87 on Android

View result in a separate tab

Test name	Executions per second
RegExp.text	23858.7 Ops/sec
StartsWith.text	22668.5 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 3 months ago):

LLMs can make mistakes. Check important info.

The benchmark you provided is aimed at comparing the performance of two different methods for checking if a URL starts with a specific set of prefixes: using JavaScript regular expressions (RegExp) versus using the `String.startsWith()` method. Here's a breakdown of what is tested and the pros and cons of each approach:

### Options Compared

1. **Regular Expression (RegExp) Test**
   - **Test Case**: `if (!regex.test(url)) console.log('passed');`
   - **Description**: This test checks whether the URL matches a predefined regular expression pattern that specifies a set of valid prefixes.
   - **Regular Expression**: The regex pattern `/^(\/nxp|\/_next\/static|\/_next\/image|\/favicon.ico)/` is used. It looks to see if the URL starts with any of these specific paths.

2. **String.startsWith() Test**
   - **Test Case**: `if (!url.startsWith('/nxp') && !url.startsWith('/_next/static') && !url.startsWith('/_next/image') && !url.startsWith('/favicon.ico')) console.log('passed');`
   - **Description**: This test uses the `String.startsWith()` method multiple times to check if the URL starts with any of the specified prefixes.

### Pros and Cons

#### Regular Expression (RegExp)
- **Pros**:
  - Flexibility: It allows for more complex matching patterns that can handle variations in the input if needed.
  - Conciseness: A single regex pattern can cover multiple cases in one go.
  
- **Cons**:
  - Performance: Regular expressions can be slower than simple string methods, especially for simpler tasks like prefix matching. The overhead of compiling and executing the regex can lead to reduced efficiency.
  - Readability: Regex can become difficult to read or understand for those who are not familiar with regex syntax.

#### String.startsWith()
- **Pros**:
  - Simplicity: This method is straightforward, making the code easier to read and understand. Each `startsWith` call explicitly checks one condition.
  - Potentially faster: For scenarios that involve checking a limited number of prefixes, using `startsWith` may perform better than regex due to its optimized nature for this specific purpose.
  
- **Cons**:
  - Verbosity: Each prefix requires a separate call to `startsWith`, which can clutter the code as the number of prefixes increases.
  - Limited to prefix checks: This method does not allow for more complex matching patterns that a regex could facilitate.

### Other Considerations

- **Performance Measurement**: The benchmark results showed executions per second for each test, with the RegExp method executing at approximately 257,374 times per second and the `startsWith` method at approximately 246,443 times per second. Although both methods exhibit high performance, this indicates that the regex approach is slightly faster in this specific test scenario. However, the difference in performance might vary based on the complexity of the regex and the length of the input strings.

- **Browser Compatibility**: Both methods are widely supported across modern browsers, making them reliable options for developers without compatibility concerns.

### Other Alternatives

- **Using Array of Prefixes**: Another alternative could involve using an array of valid prefixes and the `Array.prototype.some()` method, like so:
  
  ```javascript
  const validPrefixes = ['/nxp', '/_next/static', '/_next/image', '/favicon.ico'];
  if (!validPrefixes.some(prefix => url.startsWith(prefix))) {
      console.log('passed');
  }
  ```
  
  This would give the benefit of cleanliness in code while still remaining performant, depending on the number of prefixes.

- **Pattern Matching with `indexOf`**: One could also use a loop with `indexOf`, although in terms of performance and readability, this isn't necessarily better than the options provided.

### Conclusion

The benchmark effectively compares two approaches for prefix checking in URLs: the regular expression and the `startsWith` method. Each has its own strengths and potential drawbacks, making the choice context-dependent. The benchmarks show that even slight variations in performance can occur and should be considered in performance-critical applications. Depending on the specific use case and requirements (readability vs. complexity), developers can select the most suitable method.

Related benchmarks:

JS regexp (version: 1)

regex VS string.startsWith

Comparing performance of: RegExp.text vs StartsWith.text

Created: 3 months ago by: Registered User

Jump to the latest result

RegExp.text

StartsWith.text

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 3 months ago):