Benchmark: JS String '+' same v.s. different strings

Script Preparation code:

var nLoops = 1000;

Tests:

Same string added each loop
var fragmentToAdd = Math.random(); var str = ''; for (var i = 0; i < nLoops; i++) { // Just to equalize the work done in each test Math.random(); str += fragmentToAdd; }
Different string added each loop
var str = ''; for (var i = 0; i < nLoops; i++) { str += Math.random(); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Same string added each loop
Different string added each loop

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 world of JavaScript microbenchmarks.

**What is tested?**

The provided JSON benchmark tests two different approaches to concatenating strings in a JavaScript loop:

1. **Same string added each loop**: In this test, the same random fragment is added to the string `str` on each iteration of the loop.
2. **Different string added each loop**: In this test, a new random fragment is generated on each iteration of the loop and added to the string `str`.

The benchmark measures the performance difference between these two approaches.

**Options compared**

We have two options being compared:

1. **Using a static variable (same string)**: This approach uses the same variable (`fragmentToAdd`) on each iteration, which can lead to cache effects and potential optimization issues.
2. **Using a different variable on each iteration (different string)**: This approach generates a new random fragment on each iteration, which may lead to better performance due to reduced cache effects.

**Pros and Cons**

1. **Same string added each loop**:
	* Pros:
		+ Easier to understand and maintain, as the same variable is used consistently.
	* Cons:
		+ Potential for cache effects, which can lead to suboptimal performance.
		+ May not account for optimization opportunities that are missed due to caching.
2. **Different string added each loop**:
	* Pros:
		+ Reduces cache effects and may lead to better performance.
	* Cons:
		+ More complex code, as a new variable needs to be generated on each iteration.

**Library usage**

There is no explicit library used in this benchmark. However, the `Math.random()` function is used, which is a built-in JavaScript function that generates random numbers.

**Special JS features or syntax**

There are no special JavaScript features or syntax mentioned in this benchmark. The code uses standard JavaScript constructs and does not employ any advanced techniques like async/await or arrow functions.

**Other alternatives**

If you were to implement similar benchmarks, you might also consider testing other approaches, such as:

* Using `String.prototype +=` instead of the `+` operator.
* Using a loop with an array or object to store and reuse fragments.
* Comparing performance using different string concatenation methods (e.g., using `concat()` vs. `+=`).

Keep in mind that these alternatives might require modifications to the benchmark code to accommodate the new approach.

I hope this explanation helps you understand the JavaScript microbenchmark!

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/109.0

Browser/OS: Firefox 109 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
Same string added each loop	360294.2 Ops/sec
Different string added each loop	10157.2 Ops/sec

Related benchmarks:

JS String '+' same v.s. different strings (version: 0)

Is there a difference in performance over many iterations of string concatenation if the string being added is the same or different each time?

Comparing performance of: Same string added each loop vs Different string added each loop

Created: 9 months ago by: Guest

Jump to the latest result

Same string added each loop

Different string added each loop

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):