Benchmark: Regex vs split/join space

Script Preparation code:

var str = 'Abcd efghij klmnopqrstuv wxy Abcd efghij klmnopqrstuv wxy Abcd efghij klmnopqrstuv wxyAbcd efghij klmnopqrstuv wxy Abcd efghij klmnopqrstuv wxy Abcd efghij klmnopqrstuv wxy';

Tests:

Regex
str.replace(/\s/g, "%20");
Split and Join
str.split(' ').join('%20');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Regex
Split and Join

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

The provided JSON represents a JavaScript microbenchmark that compares two approaches to replace whitespace characters in a string: using regular expressions (`Regex`) and splitting a string into an array, joining it with a separator, and then replacing the original separator with a new one (`Split and Join`).

**Library Used: None**

There is no library used in this benchmark.

**Special JS Features/Syntax: None**

There are no special JavaScript features or syntax used in this benchmark.

**Options Compared**

The two options compared are:

1. **Regex**: This approach uses the `replace()` method with a regular expression to replace all whitespace characters (`\s`) with `%20` (ASCII code for space).
2. **Split and Join**: This approach splits the input string into an array using the `split()` method with a separator, joins it back into a string using the `join()` method with a new separator `%20`, and then replaces the original separator with the new one.

**Pros and Cons of Each Approach**

*   **Regex:**
    *   Pros:
        *   Can be more flexible and powerful for complex string replacements.
        *   Often faster than splitting and joining because it's a built-in method that can be optimized by JavaScript engines.
    *   Cons:
        *   Can be slower due to the overhead of compiling regular expressions.
        *   More error-prone if not used carefully, as incorrect regex patterns can lead to unexpected results or crashes.
*   **Split and Join:**
    *   Pros:
        *   Often faster than using regex because it avoids the overhead of compilation.
        *   Easier to understand and maintain for simple string replacements.
    *   Cons:
        *   Less flexible and powerful compared to regex, as it requires splitting the string into an array first.

**Benchmark Preparation Code**

The preparation code provided creates a test string with repeating whitespace characters (`Abcd efghij klmnopqrstuv wxy`), which will be used for both tests. The `replace()` method is called on this string using regex to replace all whitespace characters, and the `split()` and `join()` methods are also applied in the same way.

**Benchmark Result**

The latest benchmark result shows that the `Split and Join` approach outperforms the `Regex` approach, with approximately 25% more executions per second. However, keep in mind that this is just a single benchmark result, and results may vary depending on other factors like system resources and JavaScript engine versions.

**Alternatives**

Other alternatives to these approaches include:

1.  **Using String.prototype.replace() with a callback**: This approach can provide more flexibility for complex string replacements.
2.  **Using String.prototype.split() and then applying the replacement**: Similar to the split and join approach but without joining back into a string, which might be faster for larger strings.

However, these alternatives may not always outperform the original approaches in terms of execution speed.

In summary, while both approaches have their trade-offs, splitting and joining can often be a faster option for simple string replacements due to its simplicity and lack of overhead. However, when dealing with complex regex patterns or flexibility is crucial, using regular expressions might be a better choice despite the potential performance hit.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/94.0.4606.61 Safari/537.36

Browser/OS: Chrome 94 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Regex	840481.9 Ops/sec
Split and Join	1054421.5 Ops/sec

Related benchmarks:

Regex vs split/join space (version: 0)

Comparing performance of: Regex vs Split and Join

Created: 4 years ago by: Guest

Jump to the latest result

Regex

Split and Join

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):