Benchmark: RegExp replace vs String join

Tests:

RegExp replace
const priceEu = '650'.replace(/.+/, 'Price EU: $&€'); const priceUs = '715'.replace(/.+/, 'Price US: &dollar;$&');
String join
const priceEu = ['Price EU: ', '€'].join('650'); const priceUs = ['Price US: &dollar;', ''].join('715');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
RegExp replace
String join

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and its test cases.

**Benchmark Definition**

The benchmark is defined as a JSON object that contains information about the test case, such as the name, description, script preparation code, HTML preparation code, and individual test cases.

In this specific case, the benchmark definition only contains a `Name` and an empty `Description`. The `Script Preparation Code` and `Html Preparation Code` fields are also empty, which means that no additional setup or preparation is required for the test case.

**Individual Test Cases**

There are two test cases:

1. **RegExp replace**
The first test case uses a regular expression to replace a pattern in a string. The script definition is:
```javascript
const priceEu = '650'.replace(/.+/, 'Price EU: $&&euro;');
const priceUs = '715'.replace(/.+/, 'Price US: &dollar;$&');
```
In this case, the regular expression `/.+/` matches one or more characters (`+`) at the start of the string (`^`). The `replace()` method replaces all occurrences of this pattern with a new string.

2. **String join**
The second test case uses the `join()` method to concatenate two strings:
```javascript
const priceEu = ['Price EU: ', '&euro;'].join('650');
const priceUs = ['Price US: &dollar;', ''].join('715');
```
In this case, the `join()` method concatenates an array of strings with a separator (`' '`).

**Comparison and Analysis**

The two test cases compare the performance of using regular expressions (`RegExp replace`) versus string concatenation (`String join`).

**Pros and Cons**

* **Regular Expressions (RegExp Replace)**:
	+ Pros: Can be more efficient for complex pattern matching, as it avoids iterating over each character individually.
	+ Cons: Can be slower due to the overhead of compiling and executing the regular expression.
* **String Concatenation (String Join)**:
	+ Pros: Typically faster, as it avoids the overhead of compiling a regular expression.
	+ Cons: May not be suitable for complex pattern matching or when working with large datasets.

**Library and Special Features**

There is no library being used in this benchmark. However, some special JavaScript features are at play:

* The `$` character is an escape character, which means that it needs to be escaped using a backslash (`\$`) if used in a string literal.
* The `&&` operator has its usual precedence, but it's not explicitly mentioned as a special feature.

**Other Alternatives**

Some alternative approaches for the regular expression test case could include:

* Using a more efficient regular expression pattern (e.g., `\d+` instead of `.+`)
* Compiling the regular expression once and reusing it in multiple iterations
* Using an iterative approach to replace substrings, rather than using `replace()` with a global flag (`g`)

For the string concatenation test case, other alternatives could include:

* Using a more efficient string concatenation method (e.g., `Array.prototype.join()` instead of the standard `join()` method)
* Using an intermediate data structure (e.g., an array) to store the concatenated strings

Keep in mind that these alternative approaches are likely to have varying degrees of performance impact, and may not always be more efficient than the original implementation.

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.75 Safari/537.36

Browser/OS: Chrome 86 on Windows

View result in a separate tab

Test name	Executions per second
RegExp replace	583565.0 Ops/sec
String join	3449347.5 Ops/sec

Related benchmarks:

RegExp replace vs String join (version: 0)

Comparing performance of: RegExp replace vs String join

Created: 5 years ago by: Registered User

Jump to the latest result

RegExp replace

String join

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):