Benchmark: starts/endswith vs regex.test

HTML Preparation code:

<!--your preparation HTML code goes here-->

Script Preparation code:

let regex = /^hello.*$/,
    str = 'aaaaaaaaaaaaaaaaaaaaaaaaahelloaaaaaaaaaaaaaaaaaaaa',
    str2 = 'helloaaaaaaaaaaaaaaaaaaaaaaaaa'

Tests:

regex
regex.test(str) regex.test(str2)
startswith
str.startsWith('hello') str2.startsWith('hello')

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: one year ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:134.0) Gecko/20100101 Firefox/134.0

Browser/OS: Firefox 134 on Linux

View result in a separate tab

Test name	Executions per second
regex	27437076.0 Ops/sec
startswith	2445347840.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

LLMs can make mistakes. Check important info.

The benchmark defined in the provided JSON compares two string-checking approaches in JavaScript: using regular expressions (regex) versus the built-in `startsWith` method.

### Benchmark Overview:

1. **Comparison Options:**
   - **`regex.test(str)` and `regex.test(str2)`**: This tests whether the strings `str` and `str2` match the defined regular expression (regex) pattern, which checks if the strings start with "hello" followed by any characters.
   
   - **`str.startsWith('hello')` and `str2.startsWith('hello')`**: This checks if `str` and `str2` start with the substring "hello" using the string method `startsWith`.

### Benchmark Results:
- `startsWith` achieved **2,445,347,840** executions per second.
- `regex.test` achieved **27,437,076** executions per second.

### Pros and Cons of Each Approach:

#### `startsWith` Method:
**Pros:**
- **Performance**: As demonstrated in the benchmark, `startsWith` is significantly faster than regex for this specific use case.
- **Simplicity and Readability**: The `startsWith` method is straightforward and self-explanatory, making the code easier to understand.
- **No Overhead**: There is no regex engine overhead; it is simply a string method.

**Cons:**
- **Limited Flexibility**: It can only check for the start of the string; it cannot handle more complex matching scenarios.

#### Regular Expressions:
**Pros:**
- **Flexibility**: Regular expressions allow for complex patterns and are useful for matching various formats, not just fixed strings.
- **Comprehensive Use**: Regex can deal with strings in a more nuanced way (e.g., matching multiple variations or conditional patterns).

**Cons:**
- **Performance**: As shown in the benchmark, regex can be slower due to the overhead of evaluating the regex pattern, particularly for simple tasks.
- **Complexity**: Regex patterns can become difficult to read and maintain, especially for those not familiar with regex syntax.

### Other Considerations:
- **Use Case**: If the use case only requires a simple prefix check ("hello"), then `startsWith` is generally preferred due to its efficiency and clarity. In contrast, if you need to match strings based on complex patterns (e.g., validating formats, extracting parts of a string), regex would be necessary despite the performance cost.
  
- **Browser Compatibility**: Both methods are well-supported in modern browsers, but developers should check compatibility for older environments if necessary.

### Alternatives:
1. **Using String Indexing**: You could use the `indexOf` method or `substr` to manually check if the string starts with "hello". However, this is less idiomatic in modern JavaScript and typically less performant than `startsWith`.

2. **Other Regex Libraries**: For more complex scenarios requiring regex, libraries like `XRegExp` enhance regex in JavaScript, providing extended features and better performance for specific regex operations. However, these might add complexity and the same performance concerns as native regex.

3. **String.prototype.slice**: To achieve a similar functionality, one could check `str.slice(0, 5) === 'hello'`, but using `startsWith` is more semantic and better for readability.

In summary, this benchmark provides valuable insights into the performance implications of these two string-checking approaches within JavaScript. By evaluating the specific needs of the code in question, developers can choose between the simplicity and speed of `startsWith` versus the flexibility of regex based on the task at hand.

Related benchmarks:

starts/endswith vs regex.test (version: 1)

Comparing performance of: regex vs startswith

Created: one year ago by: Guest

Jump to the latest result

regex

startswith

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):