Benchmark: String.replace vs String.replaceAll

Tests:

Regex replace in place
"this is it".replace(/ /g, "+");
Regex replace stored in variable
var token = / /g; "this is it".replace(token, "+");
String replaceAll
"this is it".replaceAll(" ", "+");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Regex replace in place
Regex replace stored in variable
String replaceAll

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 10 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:126.0) Gecko/20100101 Firefox/126.0

Browser/OS: Firefox 126 on Windows

View result in a separate tab

Test name	Executions per second
Regex replace in place	7006335.0 Ops/sec
Regex replace stored in variable	6957298.5 Ops/sec
String replaceAll	16183910.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

The provided JSON represents a benchmark that compares three different approaches for replacing strings or regular expressions in JavaScript:

1. `String.replace()`
2. `String.replaceAll()` (not a standard JavaScript method, but rather a custom implementation)
3. Using a stored regular expression variable (`/ /g`)

**Options Compared:**

* **In-place replacement**: Replacing the string directly using `String.replace()` or by storing the regular expression in a variable and passing it to `String.replace()`.
* **Preparation overhead**: The time spent preparing the benchmark code, including string concatenation, assigning variables, and setting up regular expressions.

**Pros and Cons of Each Approach:**

1. **In-place replacement (String.replace())**
	* Pros:
		+ Fast and efficient, as it only iterates over the original string.
		+ No additional memory allocation or object creation required.
	* Cons:
		+ May incur higher preparation overhead due to the need to create a temporary regular expression object.
2. **Prepared replacement (String.replaceAll())**
	* Pros:
		+ Reduces preparation overhead by not requiring any setup for in-place replacement.
		+ Can be faster than in-place replacement if the string is large and the search pattern covers most of it.
	* Cons:
		+ Requires extra memory allocation and object creation, which can lead to slower performance.
3. **Storing regular expression in a variable**
	* Pros:
		+ Similar preparation overhead as prepared replacement.
		+ Can be faster than in-place replacement if the search pattern is complex or covers most of the string.
	* Cons:
		+ Requires additional memory allocation and object creation, which can lead to slower performance.

**Other Considerations:**

* The choice of regular expression pattern (`/ /g`) might impact the performance. In this case, it seems to be a simple space character replacement.
* JavaScript engines like SpiderMonkey (used in Firefox) might optimize certain aspects of these operations, such as caching or using specialized instruction sets.

**Library and Purpose:**

There is no library explicitly mentioned in the provided code snippets. However, the use of regular expressions (`/ /g`) suggests that the test is leveraging the built-in JavaScript standard library for string manipulation.

**Special JS Features/Syntax:**

None are explicitly mentioned in the provided code snippets.

Related benchmarks:

String.replace vs String.replaceAll (version: 0)

Comparing performance of: Regex replace in place vs Regex replace stored in variable vs String replaceAll

Created: 2 years ago by: Guest

Jump to the latest result

Regex replace in place

Regex replace stored in variable

String replaceAll

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 6 months ago):