Benchmark: replace string vs regexp

Script Preparation code:

var strIn = 'asdada {{ asdasd a{asdas sad}sadasd}} sadasdas} asd ad';
var strOut = '';
var regex = /{{|}}/g;

Tests:

substring
strOut = strIn.replace('{{','').replace('}}','')
regex
strOut = strIn.replace(regex, '');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
substring
regex

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 136 on Android

View result in a separate tab

Test name	Executions per second
substring	3363783.8 Ops/sec
regex	3537133.2 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark on the website MeasureThat.net. The benchmark compares two approaches to replace substrings in a string: using the `replace()` method with substring literals and using regular expressions.

**Script Preparation Code**

The script preparation code is used to set up the test environment. It defines two variables:

* `strIn`: a string containing a template with double curly brackets (`{{}}`) that will be replaced.
* `strOut`: an empty string that will be initialized later.
* `regex`: a regular expression object with the pattern `/{{|}}/g` (more on this later).

The script also includes two blank lines, which may serve as whitespace or formatting purposes.

**Html Preparation Code**

There is no HTML preparation code provided, so it's assumed that the benchmark only tests the JavaScript execution.

**Individual Test Cases**

There are two test cases:

1. **"substring"**: This test case uses the `replace()` method with substring literals to replace the substrings in `strIn`.
2. **"regex"**: This test case uses a regular expression (`regex`) to replace the substrings in `strIn`.

**Regular Expressions (Regex)**

The regex pattern `/{{|}}/g` is used to match and replace the double curly brackets (`{{}}`) in the string `strIn`. The `/g` flag at the end of the pattern ensures that all occurrences are replaced, not just the first one.

**Pros and Cons of Each Approach**

* **`replace()` method with substring literals**: This approach is straightforward and easy to read. However, it may be slower than using regular expressions for more complex replacements.
	+ Pros: Easy to understand, less overhead for simple cases.
	+ Cons: May be slower for complex replacements, limited capabilities.
* **Regular expression**: Using regular expressions provides more flexibility and power for replacing substrings, but can also lead to performance issues if not optimized properly.
	+ Pros: More flexible, powerful replacement options.
	+ Cons: Can be slower due to the complexity of regex operations.

**Other Considerations**

* Memory usage: The benchmark should consider how memory is allocated and deallocated for each approach. Using regular expressions might require more memory allocation than the `replace()` method with substring literals.
* String concatenation: In the "substring" test case, string concatenation using `''` is used to build the output string. This can lead to performance issues if done repeatedly.

**Alternative Approaches**

Other approaches to replace substrings in JavaScript include:

* **Using `String.prototype.replace()` with a function**: Instead of using substring literals or regular expressions, you could define a custom replacement function.
* **Using a library like Lodash's `replace()` method**: Libraries like Lodash provide optimized and flexible string manipulation functions that might outperform the built-in methods.

Overall, the benchmark provides an interesting comparison between two common approaches to replacing substrings in JavaScript. Understanding the pros and cons of each approach can help developers optimize their code for specific use cases.

Related benchmarks:

replace string vs regexp (version: 0)

Comparing performance of: substring vs regex

Created: 5 years ago by: Guest

Jump to the latest result

substring

regex

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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