Benchmark: Spread vs concat vs unshift (fair) to join arrays test2

Script Preparation code:

var a = [1,2,3];
var b = [4,5,6];
var c = [];

Tests:

spread
b=[...a,...b];
concat
b=a.concat(b);
unshift (forEach)
a.forEach(el => c.unshift(el)) b.forEach(el => c.unshift(el))
unshift (spread)
c.unshift(...a); c.unshift(...b);
push
var aLen = a.length; var bLen = b.length; var i = 0; for (; i < aLen; i++) { c.push(a[i]); } i = 0 for (; i < bLen; i++) { c.push(b[i]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
spread
concat
unshift (forEach)
unshift (spread)
push

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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

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Let's dive into the world of JavaScript microbenchmarks.

**What is being tested?**

The provided benchmark tests the performance of different methods to join two arrays in JavaScript:

1. Using the spread operator (`...`)
2. Using `concat()`
3. Using `unshift()` with a loop
4. Using `push()` with a loop

**Options compared**

Each test case compares the performance of one specific method against others, allowing users to compare their performance on different platforms and browsers.

*   **Spread Operator (`...`)**: This option uses the spread operator to create a new array by copying elements from one or more source arrays.
*   `concat()`: This option uses the `concat()` method to concatenate two arrays into a single array.
*   `unshift()` with a loop: This option uses `unshift()` to add one or more elements to the beginning of an array and then loops through both input arrays using `forEach`.
*   `push()` with a loop: This option uses `push()` to add elements to the end of an array and then loops through both input arrays using `forEach`.

**Pros and Cons**

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

### Spread Operator (`...`)

Pros:
*   Fast performance
*   Creates a new array, avoiding modifying the original
*   Supports multiple source arrays

Cons:
*   Only supported in modern browsers (ECMAScript 2015+)
*   May not work well with very large arrays due to memory constraints

### `concat()`

Pros:
*   Widely supported across all browsers and environments
*   Does not require a new array creation

Cons:
*   Creates a new array, which can be slower for large inputs
*   Returns a new array object instead of modifying the original

### `unshift()` with a loop

Pros:
*   Fast performance
*   Supports both input arrays without requiring them to be in order

Cons:
*   Uses `forEach`, which may have performance implications due to its nature
*   Not as straightforward or readable as other methods

### `push()` with a loop

Pros:
*   Fast performance
*   Does not require additional array creation

Cons:
*   May not work well if both arrays are large and need to be joined in the correct order
*   Uses `forEach`, which may have performance implications due to its nature

**Library Used**

No specific library is used in this benchmark, as it relies on built-in JavaScript methods.

**Special JS Features or Syntax**

The test cases use some modern features:

*   **Rest Operator (`...`)**: The spread operator was introduced in ECMAScript 2015 and allows for creating new arrays from source values.
*   `forEach()`: This method is used to iterate over the elements of an array. It's a part of the ECMAScript specification.

**Other Alternatives**

If you're looking for alternative methods to join arrays, consider:

*   **Array.prototype.reduce()**: While more complex and less straightforward than the provided options, `reduce()` can be used to accumulate values from both input arrays.
*   **Using `Array.prototype.concat()` with a spread operator (`...`)**: This option would concatenate two arrays using `concat()` followed by spreading one of the arrays into the result.

These alternatives offer different trade-offs in terms of performance, readability, and maintainability. When choosing an approach for your specific use case, consider factors like input size, performance requirements, and code readability.

Related benchmarks:

Spread vs concat vs unshift (fair) to join arrays test2 (version: 0)

Comparing the performance of spread, vs concat vs unshift to join two arrays

Comparing performance of: spread vs concat vs unshift (forEach) vs unshift (spread) vs push

Created: 3 years ago by: Registered User

Jump to the latest result

spread

concat

unshift (forEach)

unshift (spread)

push

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):