Benchmark: replace vs split and join

replace vs split and join (version: 0)

Test the performance of replace() vs substring() vs slice() when replacing a char at the beginning of a (in this case uri query-)string that may or may not be there. Added the combined brackets[ ] + substr() method, since it's always the first char we wan't to pop off. Inspired by https://jsperf.com/replace-or-substr. Note: could not get 'let' and 'const' to work. Well, too bad...

Comparing performance of: `replace inline regex vs replace compiled regex var vs split and join`

Created: 4 years ago by: Guest

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Script Preparation code:

var strIn = '?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it?this=a+test&that=just+it';
var strOut = 'some';
var regex = /that/g;

Tests:

replace inline regex
strOut = strIn.replace(/that/g, '');
replace compiled regex var
strOut = strIn.replace(regex, '');
split and join
strOut = strIn.split('that').join('some')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
replace inline regex
replace compiled regex var
split and join

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:138.0) Gecko/20100101 Firefox/138.0

Browser/OS: Firefox 138 on Mac OS X 10.15

View result in a separate tab

replace inline regex

397K/s

replace compiled regex var

395K/s

split and join

319K/s

View exact numbers

Test name	Executions per second
✓ replace inline regex	397,091 Ops/sec
replace compiled regex var	395,376 Ops/sec
split and join	319,348 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition, test cases, and results.

**Benchmark Definition**

The benchmark measures the performance of three different approaches to replace a substring in a string:

1. `strOut = strIn.replace(/that/g, '');`
2. `strOut = strIn.replace(regex, '');`
3. `strOut = strIn.split('that').join('some')`

These approaches are tested with two variations: using inline regular expressions (`/that/g`) and compiling the regular expression into a variable (`regex`).

**Options Compared**

The benchmark compares the following options:

1. **Inline Regular Expression**: Replacing the substring directly in the `replace()` method.
2. **Compiled Regular Expression**: Compiling the regular expression into a variable before using it in the `replace()` method.
3. **Split and Join**: Using the `split()` method to split the string at the target substring, and then joining the resulting parts back together with a new separator.

**Pros and Cons**

1. **Inline Regular Expression**:
	* Pros: Simple, easy to read, and efficient for small substrings.
	* Cons: Can be slower than compiled regular expressions for larger substrings due to the overhead of parsing the regex pattern.
2. **Compiled Regular Expression**:
	* Pros: Faster performance for large substrings, as the regex is pre-compiled and can be reused.
	* Cons: More complex and harder to read, especially for simple cases.
3. **Split and Join**:
	* Pros: Simple and efficient, especially for larger substrings or when the target substring is not present at the beginning of the string.
	* Cons: May create intermediate arrays, which can be memory-intensive.

**Library and Syntax**

The benchmark uses regular expressions (regex) as part of its test cases. Regular expressions are a powerful tool for pattern matching in JavaScript, but they can also introduce overhead due to their complexity.

The benchmark does not use any special JavaScript features or syntax beyond the standard language.

**Other Alternatives**

For this specific benchmark, alternative approaches could include:

* Using a library like `string.prototype.replaceAll()` (available in modern browsers) which provides an efficient and readable way to replace substrings.
* Using a library like `regex- escape` or `js-string-replace` for more advanced regex patterns and optimizations.

However, these alternatives would require significant changes to the benchmark definition and test cases.

I hope this explanation helps software engineers understand the benchmark and its options!