Benchmark: RegEx.match vs. startWith2

Script Preparation code:

var string = "Hello world!";
var regex = /Hello/;

Tests:

String.startsWith
string.startsWith("Hello");
String.match
string.match(regex);
startsWith
string.startsWith("Hello");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
String.startsWith
String.match
startsWith

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:135.0) Gecko/20100101 Firefox/135.0

Browser/OS: Firefox 135 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
String.startsWith	1972865920.0 Ops/sec
String.match	39209064.0 Ops/sec
startsWith	1977266048.0 Ops/sec

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

LLMs can make mistakes. Check important info.

The benchmark provided compares the performance of two different methods for checking if a string begins with a specified substring: `String.startsWith()` and `String.match()` using a regular expression. Here's a detailed breakdown of the benchmark, the tested approaches, their pros and cons, and other considerations:

### Tested Approaches

1. **String.startsWith()**
   - **Code:** `string.startsWith("Hello");`
   - **Purpose:** This method checks if the string starts with a specified substring. It returns `true` or `false`.
   - **Pros:**
     - Simple and straightforward to use.
     - Optimized for performance as it is a fundamental string method.
     - More readable than regular expressions for substring checks.
   - **Cons:**
     - Limited to checking the starting substring only; does not support complex patterns.

2. **String.match()**
   - **Code:** `string.match(regex);` where `regex` is defined as `/Hello/`.
   - **Purpose:** This method retrieves the matches when matching a string against a regular expression.
   - **Pros:**
     - Supports more complex patterns, allowing for flexible string matching.
     - Can find all occurrences or elements that meet specific criteria based on regex rules.
   - **Cons:**
     - Generally slower than `startsWith()` for this specific use case due to the overhead involved in pattern matching.
     - The syntax can be less readable, especially for those unfamiliar with regular expressions.

### Alternatives

Other alternatives to these methods could include:

- **Using `indexOf()`:** You could check the index of a substring and determine if it starts at position zero:
  ```javascript
  string.indexOf("Hello") === 0;
  ```
  - **Pros:** A long-standing method in JavaScript; very readable.
  - **Cons:** Not as efficient as `startsWith()` for this specific task as it returns the index rather than a boolean result.

- **Using regular expressions with anchors:** A regex can also be used directly to match the start of a string:
  ```javascript
  /^Hello/.test(string);
  ```
  - **Pros:** More flexible than `startsWith()` and can be easily modified for different patterns.
  - **Cons:** More complex and likely slower than the dedicated `startsWith()` method.

### Test Results Summary

The benchmark results indicate the performance of each method in terms of executions per second:

- **`startsWith`**: 1,977,266,048 executions/second
- **`String.startsWith`**: 1,972,865,920 executions/second
- **`String.match`**: 39,209,064 executions/second

### Conclusion

The results show that the two `startsWith` variants are significantly faster than using `match()` with a regex, affirming the efficiency of dedicated string methods for simple checks. While `String.match()` offers more versatility for complex matching scenarios, it is generally inappropriate for straightforward prefix checks due to its performance overhead. For engineers, opting for `startsWith()` is preferred when dealing with simple substring checking, while `match()` should be reserved for cases demanding regular expression capabilities.

Related benchmarks:

RegEx.match vs. startWith2 (version: 1)

a

Comparing performance of: String.startsWith vs String.match vs startsWith

Created: one year ago by: Guest

Jump to the latest result

String.startsWith

String.match

startsWith

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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