Benchmark: JS String '+' same v.s. different strings 2

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 var randomString = String(Math.random()); str += fragmentToAdd; }
Different string added each loop
var str = ''; for (var i = 0; i < nLoops; i++) { var randomString = String(Math.random()); str += randomString; }

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 25 days ago):

LLMs can make mistakes. Check important info.

**Understanding the Benchmark**

The provided JSON represents a JavaScript microbenchmark test case on MeasureThat.net. The benchmark compares the performance of two approaches for string concatenation: using the same string (`fragmentToAdd`) added to another variable (`str`) repeatedly, and using different strings in each iteration.

**Options Compared**

Two options are being compared:

1. **Using the same string (`fragmentToAdd`) added to another variable (`str`) repeatedly**: This approach involves adding a fixed value (`fragmentToAdd`) to the `str` variable multiple times.
2. **Using different strings in each iteration**: In this approach, a new random string is generated for each iteration and concatenated with the existing `str`.

**Pros and Cons**

### Using the same string

Pros:

* This approach can be more efficient since it avoids generating a new random string for each iteration, which can reduce memory allocation and garbage collection overhead.
* It's likely to have better cache locality, as the same value is being added repeatedly.

Cons:

* If the `fragmentToAdd` value is large or complex, this approach may still incur significant overhead due to repeated allocations and assignments.
* The performance benefit of using a fixed string might not be noticeable for small values or short iterations.

### Using different strings

Pros:

* This approach can take advantage of the fact that JavaScript engines are optimized for generating random numbers. The random number generation process is likely to be more efficient than generating a new string each time.
* It allows the engine to optimize for the specific use case, potentially leading to better performance.

Cons:

* Generating a new random string for each iteration incurs additional overhead due to memory allocation and garbage collection.
* Cache locality is likely to be poor, as different values are being added repeatedly.

**Library Use**

None of the provided benchmark definitions explicitly use any libraries. However, it's worth noting that some JavaScript engines might provide optimized functions or built-in support for string concatenation that could affect the results.

**Special JS Feature/Syntax**

The benchmark uses a feature commonly found in JavaScript: `String()` and arithmetic operations (`Math.random()`) to generate random numbers. This is a standard way to generate randomness in JavaScript, but it's worth noting that some newer features or engines might provide alternative methods for generating randomness.

**Alternatives**

Other alternatives for string concatenation include:

1. **Array.join()**: Instead of concatenating strings directly, you can create an array of strings and use `join()` to concatenate them.
2. **Template literals**: A relatively new feature introduced in ECMAScript 2015 (ES6), template literals provide a more efficient way to concatenate strings.
3. **`Buffer` API**: In Node.js, the `Buffer` API provides an alternative way to work with binary data and string concatenation.

These alternatives might offer performance benefits or improved readability, but they're not directly related to the specific comparison being made in this benchmark.

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	355105.4 Ops/sec
Different string added each loop	9863.4 Ops/sec

Related benchmarks:

JS String '+' same v.s. different strings 2 (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 25 days ago):