Benchmark: concat vs spread perfs

Tests:

Spread
const a = [1, 2, 3, 4 ,5, 6, {a:1}]; const b = [7, 8, 9, 10, 11, 12, {b:2}] const c = [...a, ...b];
concat
const a = [1, 2, 3, 4 ,5, 6, {a:1}]; const b = [7, 8, 9, 10, 11, 12, {b:2}] const c = a.concat(b);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread
concat

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the provided benchmark and its test cases.

**Benchmark Overview**

The benchmark, named "concat vs spread perfs", compares the performance of two approaches: concatenation (`concat`) and spreading (`...`) when creating an array from multiple sources.

**Test Cases**

There are two individual test cases:

1. **"Spread"`**
	* The benchmark definition code is:
```javascript
const a = [1, 2, 3, 4 ,5, 6, {a:1}];
const b = [7, 8, 9, 10, 11, 12, {b:2}];
const c = [...a, ...b];
```
	* In this test case, an array `c` is created by spreading the contents of two arrays `a` and `b`, using the spread operator (`...`). This creates a new array with all elements from both `a` and `b`.
2. **"concat"`**
	* The benchmark definition code is:
```javascript
const a = [1, 2, 3, 4 ,5, 6, {a:1}];
const b = [7, 8, 9, 10, 11, 12, {b:2}];
const c = a.concat(b);
```
	* In this test case, an array `c` is created by concatenating the contents of two arrays `a` and `b`, using the `concat()` method.

**Library Usage**

In both test cases, no external libraries are used.

**Special JS Features or Syntax**

There's a subtle difference in how these approaches handle nested objects:

* In the "Spread" case, when spreading an object `{a:1}`, it will be spread as a key-value pair into the new array. This is because JavaScript uses the "object spread" syntax (`{a:1}`) to create an object from a single value.
* In the "concat" case, when concatenating `a` and `b`, it will concatenate the arrays as individual elements, without spreading objects.

This difference in behavior might have performance implications depending on the specific use case.

**Pros and Cons of Each Approach**

Here are some pros and cons for each approach:

**Concatenation (concat)**

Pros:

* Easy to understand and implement
* Works well with primitive values (e.g., numbers, strings)

Cons:

* Can be slower due to the overhead of creating a new array and copying elements
* May not work as expected when dealing with nested objects or complex data structures

**Spreading (...)**

Pros:

* Creates a new array with all elements from both arrays
* Works well with nested objects, spreading them as key-value pairs

Cons:

* Can be slower due to the overhead of creating a new array and copying elements
* May not work as expected when dealing with primitive values or certain data types

**Other Alternatives**

If you're looking for alternative approaches, consider:

1. **Array.prototype.push()**: Instead of concatenating arrays using `concat()`, you can use `push()` to add individual elements to an array.
2. **Array.prototype.set()**: In modern browsers, you can use the `set()` method on a typed array (e.g., `Int32Array`) to perform more efficient element copying.
3. **Native spread operators for specific data types**: Some data types have optimized spread operators, such as:
	* `Map` objects
	* `Set` collections
	* `TypedArrays`

Keep in mind that the best approach depends on your specific use case and performance requirements.

I hope this explanation helps you understand the benchmark and its test cases!

Related benchmarks:

concat vs spread perfs (version: 0)

Comparing performance of: Spread vs concat

Created: 5 years ago by: Guest

Jump to the latest result

Spread

concat

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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