Benchmark: array spread operator vs concat fix

Script Preparation code:

var a = Array.from({length: 1000}).map((_, i)=>`${i}`);
var b = Array.from({length: 2000}).map((_, i)=>`${i}`);
var aSmall = ['a', 'b', 'c', 'd'];
var bSmall = ['e', 'f', 'g', 'h', 'i'];

Tests:

spread big
const c = [...a, ...b];
concat big
const c = a.concat(b);
spread small
const c = [...aSmall, ...bSmall];
concat small
const c = aSmall.concat(bSmall);
spread big smal
const c = [...b, ...bSmall];
spread small big
const c = [...bSmall, ...b];
concat big small
const c = b.concat(bSmall);
concat small big
const c = bSmall.concat(b);
shallow copy spread
const c = [...b];
shallow copy concat
const c = [].concat(b);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
spread big
concat big
spread small
concat small
spread big smal
spread small big
concat big small
concat small big
shallow copy spread
shallow copy concat

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

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

**Benchmark Definition**

The benchmark is testing two ways to concatenate (merge) arrays in JavaScript:

1. Using the spread operator (`[...array]`)
2. Using the `concat()` method

The benchmark creates two large arrays `a` and `b`, each with a different number of elements, and then tests the performance of concatenating them using both methods.

**Options Compared**

The options being compared are:

1. Spread operator (`[...array]`)
2. `concat()` method
3. Shallow copying an array using `Array.prototype.slice()` or spreading it (`[...]`)

**Pros/Cons**

Here's a brief summary of the pros and cons of each option:

* **Spread Operator (`[...array]`)**
	+ Pros: concise, efficient, and easy to read.
	+ Cons: requires JavaScript 3.0+, and may not work as expected in older browsers or environments with limited support for spread operators.
* **`concat()` method**
	+ Pros: widely supported across different browsers and environments, doesn't require a modern JavaScript version.
	+ Cons: less concise and might be slightly slower than the spread operator.
* **Shallow Copying using `Array.prototype.slice()`**
	+ Pros: simple and easy to understand.
	+ Cons: creates a new array reference, which can lead to unexpected behavior if modified by external code.
* **Spreading an Array (`[...]`)**
	+ Pros: allows for shallow copying while still being concise.
	+ Cons: requires JavaScript 3.0+, and might not work as expected in older browsers or environments with limited support for spread operators.

**Other Considerations**

* The benchmark creates large arrays `a` and `b`, which can impact performance. Using smaller arrays would reduce the overhead of array concatenation.
* The benchmark doesn't account for the number of iterations or the context in which these operations are used. Real-world scenarios might involve more complex logic, such as iterating over an array and concatenating elements.

**Conclusion**

The benchmark primarily compares the efficiency of using the spread operator versus the `concat()` method. While the spread operator is generally faster and more concise, it's essential to consider the specific use case, the JavaScript version being used, and potential browser limitations before making a decision. Shallow copying or spreading an array can be viable alternatives in certain situations, but may require additional considerations.

Keep in mind that this benchmark might not reflect real-world scenarios where other factors like memory management, garbage collection, or parallel processing might impact performance.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.6 Safari/605.1.15

Browser/OS: Safari 16 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
spread big	79820.9 Ops/sec
concat big	309018.8 Ops/sec
spread small	4713086.5 Ops/sec
concat small	5659846.5 Ops/sec
spread big smal	119414.1 Ops/sec
spread small big	111095.2 Ops/sec
concat big small	420127.7 Ops/sec
concat small big	413044.8 Ops/sec
shallow copy spread	189245.6 Ops/sec
shallow copy concat	428604.3 Ops/sec

Related benchmarks:

array spread operator vs concat fix (version: 1)

Comparing performance of: spread big vs concat big vs spread small vs concat small vs spread big smal vs spread small big vs concat big small vs concat small big vs shallow copy spread vs shallow copy concat

Created: one year ago by: Registered User

Jump to the latest result

spread big

concat big

spread small

concat small

spread big smal

spread small big

concat big small

concat small big

shallow copy spread

shallow copy concat

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):