Benchmark: replace nth occurrence

Script Preparation code:

var text = "fo".repeat(2000)
var oldText = "o"
var newText = "u"
var oldTextRegexp = new RegExp(oldText, 'g')
var occurrence = 700

Tests:

repeat unitl
var substr var i = occurrence var result = text while ((substr = oldTextRegexp.exec(text)) !== null) { if (--i === 0) { result = text.slice(0, substr.index) + newText + text.slice(oldTextRegexp.lastIndex) break; } }
replace callback
var i = 0 var result = text.replace(oldTextRegexp, function (match) { ++i if (i === occurrence) { return newText } else { return match } })

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
repeat unitl
replace callback

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:80.0) Gecko/20100101 Firefox/80.0

Browser/OS: Firefox 80 on Ubuntu

View result in a separate tab

Test name	Executions per second
repeat unitl	35852.2 Ops/sec
replace callback	8371.4 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the benchmark and explain what's being tested, compared, and its pros and cons.

**Benchmark Overview**

The benchmark is designed to measure the performance of replacing an nth occurrence of a substring in a large text string using two different approaches:

1. **While loop**: This approach uses a while loop to iterate over each occurrence of the old text, and updates the result when the nth occurrence is found.
2. **String replace method with callback**: This approach uses the `replace()` method with a callback function that increments a counter for each match.

**Options Compared**

The benchmark compares two different approaches:

1. **While loop**
2. **String replace method with callback**

**Pros and Cons of Each Approach**

**While Loop (Repeat Unitl)**

Pros:

* Allows precise control over the iteration process
* Can be optimized for specific use cases

Cons:

* Can be slower due to the overhead of the while loop
* Requires manual management of indices and string slicing

**String Replace Method with Callback (Replace Callback)**

Pros:

* Often faster than traditional `replace()` method due to optimized caching mechanisms in modern browsers
* Simplifies code by using a single function for both substitution and replacement logic

Cons:

* May have limitations in terms of flexibility and control over the iteration process
* Can lead to unexpected behavior if not used carefully (e.g., handling edge cases)

**Library and Special JS Features**

The benchmark uses the `RegExp` object, which is a built-in JavaScript library for working with regular expressions. The `exec()` method is used to find all occurrences of the old text in the string.

No special JavaScript features are explicitly mentioned in the benchmark, but it's worth noting that some modern browsers have optimizations and APIs specifically designed for performance-critical string manipulation tasks (e.g., WebAssembly for JavaScript).

**Other Alternatives**

Alternative approaches to replacing an nth occurrence could include:

* Using `Array.prototype.indexOf()` or `String.prototype.indexOf()` with a custom implementation
* Implementing a custom algorithm using a different data structure (e.g., a Bloom filter)
* Utilizing Web Assembly (WASM) or other low-level optimizations for string manipulation

Keep in mind that these alternatives might not be as efficient or well-supported as the `while` loop and `replace()` method with callback approaches used in this benchmark.

Related benchmarks:

replace nth occurrence (version: 0)

Comparing performance of: repeat unitl vs replace callback

Created: 4 years ago by: Registered User

Jump to the latest result

repeat unitl

replace callback

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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