Benchmark: substring vs regex

Script Preparation code:

var location = "www.example.com";

Tests:

substring
var str=location; if (str.substring(0, 4)=="www.") str = str.substring(4);
regex
var str=location.replace(/^www\./,'');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
substring
regex

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 23 days ago):

LLMs can make mistakes. Check important info.

Let's break down the benchmark definition and test cases to understand what's being tested.

**Benchmark Definition JSON**

The provided JSON represents a JavaScript microbenchmark, which is a small, self-contained piece of code designed to measure the performance of specific JavaScript features or syntax. In this case, the benchmark is testing two approaches:

1. **Substring Method**: This approach uses the `substring()` method to extract a portion of a string.
2. **Regular Expression (Regex) Method**: This approach uses a regex pattern to match and replace the first 4 characters of the string.

**Script Preparation Code**

The script preparation code is a simple JavaScript statement that assigns the URL `www.example.com` to a variable named `location`.

**Html Preparation Code**

There is no HTML preparation code provided, which means that the benchmark is focused solely on the JavaScript execution.

**Individual Test Cases**

The test cases are defined as individual benchmarks. Each benchmark defines a specific JavaScript code snippet that will be executed repeatedly to measure its performance.

1. **Substring Method**
```javascript
var str = location;
if (str.substring(0, 4) == "www.") str = str.substring(4);
```
This code checks if the first 4 characters of the `location` string match "www." using the `substring()` method. If they do, it replaces the first 4 characters with an empty string.

2. **Regex Method**
```javascript
var str = location.replace(/^www\./,'');
```
This code uses a regex pattern to replace the first 4 characters of the `location` string with an empty string. The regex pattern `/^www\./` matches the first 4 characters of the string (`wwww.`).

**Library Used**

There is no explicit library mentioned in the benchmark definition, but it appears that the `replace()` method and the `substring()` method are being used as part of the JavaScript Standard Library.

**Special JS Features or Syntax**

There are no special JavaScript features or syntax used in this benchmark. The code snippets only use standard JavaScript methods and operators.

**Pros and Cons of Different Approaches**

The two approaches being tested have different performance characteristics:

* **Substring Method**:
	+ Pros: Can be more efficient for small strings, as it avoids creating a new regex object.
	+ Cons: Can be slower for larger strings, as it involves multiple function calls and string slicing.
* **Regex Method**:
	+ Pros: Can be faster for larger strings, as it uses an optimized regex engine and avoids creating intermediate results.
	+ Cons: May have performance overhead due to the creation of a new regex object.

**Other Alternatives**

There are other ways to achieve similar results using different approaches:

* Using string manipulation techniques, such as concatenation or slicing, instead of `substring()`.
* Using regex patterns with capture groups and backreferences to match and replace larger portions of the string.
* Using regular expression libraries like RegEx.js or regex-bits.

It's worth noting that the choice of approach depends on the specific requirements and constraints of the use case. In general, using optimized JavaScript methods and avoiding unnecessary overhead can lead to better performance.

Latest run results:

Run details: (Test run date: 6 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.135 Safari/537.36 Edge/12.10240

Browser/OS: Chrome 42 on Windows

View result in a separate tab

Test name	Executions per second
substring	10804928.0 Ops/sec
regex	5617530.5 Ops/sec

Related benchmarks:

substring vs regex (version: 0)

Comparing performance of: substring vs regex

Created: 7 years ago by: Guest

Jump to the latest result

substring

regex

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 23 days ago):