Benchmark: string concatenation += vs Array.prototype.join()

Tests:

+=
let s = ''; for (let i = 0; i < 10000; ++i) { s += i; } const t = s;
Array.prototype.join
let s = []; for (let i = 0; i < 10000; ++i) { s.push(i); } const t = s.join('');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
+=
Array.prototype.join

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/113.0

Browser/OS: Firefox 113 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
+=	3700.6 Ops/sec
Array.prototype.join	6810.6 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the benchmark definition and test cases to explain what's being tested, compared options, pros/cons, and other considerations.

**Benchmark Definition**

The provided JSON represents a JavaScript microbenchmark that tests two approaches for string concatenation:

1. Using the `+=` operator: `s += i;`
2. Using `Array.prototype.join()`: `s.push(i); s.join('');`

Both approaches aim to concatenate 10,000 strings of increasing integers into a single string.

**Test Cases**

There are two test cases:

**Case 1:** `+=` (string concatenation using the `+=` operator)

* The benchmark definition is: `let s = ''; for (let i = 0; i < 10000; ++i) { s += i; } const t = s;`
* This approach uses a simple loop to concatenate strings, which can lead to memory allocation and deallocation overhead due to the creation of temporary strings.

**Case 2:** `Array.prototype.join()`

* The benchmark definition is: `let s = []; for (let i = 0; i < 10000; ++i) { s.push(i); } const t = s.join('');`
* This approach uses an array to store the integers, and then joins them into a single string using `Array.prototype.join()`. This method is more efficient than the `+=` operator because it avoids creating temporary strings.

**Comparison**

The benchmark tests these two approaches for string concatenation:

* **Efficiency:** `Array.prototype.join()` is likely to be faster because it avoids the overhead of memory allocation and deallocation.
* **Memory usage:** The `+=` operator approach may consume more memory due to the creation of temporary strings, while `Array.prototype.join()` uses a single array to store the integers.

**Pros and Cons**

* `+=` (string concatenation using the `+=` operator):
	+ Pros: simple implementation, easy to understand.
	+ Cons: inefficient due to memory allocation and deallocation overhead.
* `Array.prototype.join()`: 
	+ Pros: efficient, avoids temporary string creation.
	+ Cons: may have a higher initial overhead due to array creation.

**Other Considerations**

* **Libraries:** Neither test case uses any external libraries. However, if the benchmark were to include a library like Lodash or Ramda, it would introduce additional complexity and potential optimization opportunities.
* **Special JS features/syntax:** There are no special JavaScript features or syntax used in these benchmarks.

**Alternatives**

Other alternatives for string concatenation could include:

* Using `String.fromCharCode()` to create individual characters and then joining them
* Using a template string (introduced in ECMAScript 2015) to concatenate strings
* Using a library like Lodash's `_.string` methods, which provide optimized string manipulation functions

These alternatives may offer different trade-offs between efficiency, memory usage, and complexity.

Related benchmarks:

string concatenation += vs Array.prototype.join() (version: 0)

Comparing performance of: += vs Array.prototype.join

Created: one year ago by: Guest

Jump to the latest result

+=

Array.prototype.join

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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