Benchmark: replace vs substring

replace vs substring (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: substring and substring vs replace inline regex

Created: 3 years ago by: Guest

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Script Preparation code:

var strIn = '#Allocation';
var strOut = '';

Tests:

substring and substring
strOut = strIn.substr(1);
replace inline regex
strOut = strIn.replace('#', "");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
substring and substring
replace inline regex

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 9 days ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36

Browser/OS: Chrome 131 on Windows

View result in a separate tab

Test name	Executions per second
substring and substring	10310201.0 Ops/sec
replace inline regex	8905305.0 Ops/sec

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

LLMs can make mistakes. Check important info.

**Overview**

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks. The provided JSON represents a benchmark test case, which compares the performance of three different methods: `replace()`, `substring()`, and `slice()` when replacing a character at the beginning of a string.

**What is being tested**

The benchmark tests how quickly each method can replace or extract a character from a string. In this specific case, the character to be replaced is '#', and the string starts with '#Allocation'. The benchmark measures the execution time for each method.

**Options compared**

There are three methods being compared:

1. `replace()`: This method replaces all occurrences of a specified pattern (in this case, '#') with another value (an empty string). It's a built-in JavaScript method that can handle regular expressions.
2. `substring()`: This method extracts a section of a string and returns it. In this case, it's used to extract the substring starting from index 1 (i.e., after the first character '#').
3. `slice()`: This method extracts a section of a string and returns it. Like `substring()`, it's used to extract the substring starting from index 1.

**Pros and Cons**

* `replace()`:
	+ Pros: Can handle regular expressions, efficient for replacing multiple occurrences.
	+ Cons: May be slower than other methods when dealing with single character replacements due to overhead of regular expression parsing.
* `substring()`:
	+ Pros: Fast and lightweight, suitable for single character replacements.
	+ Cons: Requires indexing into the string, which can lead to slow performance for large strings.
* `slice()`: This method is not explicitly mentioned in the benchmark definition. However, it's likely being used as a shorthand for `substring()` with an offset of 1.

**Library and syntax**

There are no external libraries used in this benchmark. The only special JavaScript feature or syntax used is the use of `let` and `const`, which are not working as expected (as mentioned in the benchmark definition).

**Other alternatives**

If you wanted to test other methods for replacing a character at the beginning of a string, some alternative approaches could include:

* Using a custom implementation with a loop to iterate through the characters.
* Using a library like Lodash or Ramda for more advanced string manipulation functions.
* Using a template literal with an empty string replacement.

However, it's worth noting that `replace()` and `substring()` are both built-in methods in JavaScript, making them efficient and well-suited for this type of benchmark.

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