Benchmark: string split vs string substring

Script Preparation code:

var s1 = "foo|bar|test";

Tests:

Array.split
var n1 = s1.split('|'); console.log(n1.slice(1).join('|'))
Substring
var pip = s1.indexOf('|'); console.log(s1.substring(pip));

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array.split
Substring

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):

LLMs can make mistakes. Check important info.

Let's dive into the explanation of what is being tested in this JavaScript microbenchmark.

**Overview**

The benchmark tests two different approaches to splitting a string: `Array.split` and `String.substring`. The test inputs are identical, with a single string `s1` containing multiple pipe (`|`) characters. The goal is to measure which approach performs better in terms of execution time.

**Approaches being compared**

There are two primary approaches being tested:

1. **`Array.split()`**: This method splits the input string into an array of substrings, using the pipe character as the separator. The resulting array is then processed further (in this case, `slice(1)` is used to remove the first element and `join('|')` is used to concatenate the remaining elements).
2. **`String.substring()`**: This method returns a new string that starts at the specified index (0-based) and continues to the end of the original string.

**Pros and Cons**

**`Array.split()`**:

* Pros:
	+ Can handle multiple separators (not just pipes)
	+ More concise code
	+ Can be used with additional methods (e.g., `filter()`, `map()`)
* Cons:
	+ Requires creating an array, which can lead to memory allocation overhead
	+ May not be as efficient for very large input strings

**`String.substring()`**:

* Pros:
	+ Only uses a single string operation, reducing memory allocation overhead
	+ Can be more cache-friendly due to less memory allocation
* Cons:
	+ Less concise code compared to `Array.split()`
	+ May not handle multiple separators well

**Other considerations**

* **Cache efficiency**: The browser's cache can significantly impact the execution time of this benchmark. Different browsers may have varying levels of cache efficiency, which could affect the results.
* **Garbage collection**: JavaScript engines have garbage collection mechanisms that can impact performance. For example, if the engine has to collect garbage during the test, it may introduce overhead.
* **Browser-specific optimizations**: Some browsers (e.g., Firefox) have specific optimizations for string manipulation, which could influence the results.

**Library usage**

None of the code uses any external libraries beyond the standard JavaScript library.

**Special JS feature or syntax**

There is no special JavaScript feature or syntax being used in this benchmark. However, it's worth noting that modern JavaScript engines often include experimental features (e.g., `const` support) or ES6+ features like `let` and `const`. This benchmark does not use any of these features.

**Alternatives**

Other alternatives for string splitting include:

* **Regular expressions**: Using a regular expression to split the string can be more flexible, but may also introduce overhead due to pattern matching.
* **String.match()**: This method returns an array of matches, which can be used as an alternative to `Array.split()`.

Keep in mind that these alternatives are not typically used for simple string splitting tasks and may have additional overhead or complexity.

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:97.0) Gecko/20100101 Firefox/97.0

Browser/OS: Firefox 97 on Windows

View result in a separate tab

Test name	Executions per second
Array.split	40642.7 Ops/sec
Substring	34666.9 Ops/sec

Related benchmarks:

string split vs string substring (version: 0)

Comparing performance of: Array.split vs Substring

Created: 4 years ago by: Guest

Jump to the latest result

Array.split

Substring

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 26 days ago):