Benchmark: concat vs push in various ways

Tests:

concat
let x = []; let y = [1, 2, 3, 4, 5, 6, 7]; for (let ii = 0; ii < 1000; ii++) { x = x.concat(y); }
push with rest params
let x = []; let y = [1, 2, 3, 4, 5, 6, 7]; for (let ii = 0; ii < 1000; ii++) { x.push(...y); }
push in for loop
let x = []; let y = [1, 2, 3, 4, 5, 6, 7]; for (let ii = 0; ii < 1000; ii++) { for (let item of y) { x.push(item); } }
push with forEach
let x = []; let y = [1, 2, 3, 4, 5, 6, 7]; for (let ii = 0; ii < 1000; ii++) { y.forEach(num => x.push(num)); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
concat
push with rest params
push in for loop
push with forEach

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 break down the provided benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark compares different approaches for adding elements to an array in JavaScript:

1. `concat`
2. `push` with rest parameters (`...`)
3. `push` inside a `for` loop
4. `push` with `forEach`

**Library Usage**

None of the test cases explicitly use any external libraries.

**Special JS Features/Syntax**

The benchmark uses several special JavaScript features:

1. **Rest Parameters (`...`)**: Introduced in ECMAScript 2015, rest parameters allow a function to accept an arbitrary number of arguments, which can be accessed as an array.
2. `for...of` loop with `push`: This is a relatively recent feature introduced in ECMAScript 2017.
3. `forEach()` method: This is a built-in JavaScript method for iterating over arrays.

**Options Being Compared**

The benchmark compares the performance of each approach:

1. `concat`: Using the `concat()` method to add elements to an array.
2. `push` with rest parameters (`...`): Using the spread operator (`...`) to add all elements from another array to a target array using `push()`.
3. `push` inside a `for` loop: Iterating over each element of an array and adding it to the target array using `push()`.
4. `push` with `forEach()` method: Using `forEach()` to iterate over each element of an array and add it to the target array using `push()`.

**Pros and Cons of Each Approach**

Here's a brief summary:

1. **concat**:
	* Pros: Simple, straightforward approach.
	* Cons: Can be slow for large arrays due to the creation of a new array.
2. **Push with rest parameters (`...`)**:
	* Pros: Efficient way to add all elements from another array using `push()`.
	* Cons: Requires support for rest parameters in the browser being tested (Chrome 86).
3. **Push inside a `for` loop**:
	* Pros: Allows control over iteration, but can be slower due to the overhead of the loop.
	* Cons: Less readable and less efficient than using `forEach()` or `push` with rest parameters.
4. **Push with `forEach()` method**:
	* Pros: More readable than a custom loop, and efficient for large arrays.
	* Cons: Requires support for the `forEach()` method in the browser being tested (Chrome 86).

**Other Considerations**

1. **Array Iteration**: The benchmark assumes that iterating over an array using `for...of` loops or `forEach()` is more efficient than a custom loop. This is generally true, but the performance difference may be negligible for small arrays.
2. **Browser Support**: The benchmark uses Chrome 86 as the test browser, which means that rest parameters and `forEach()` method are required for the benchmarks to work.

**Alternatives**

Other approaches for adding elements to an array in JavaScript include:

1. Using `Array.prototype.push.apply()`
2. Using a `for` loop with indexing (e.g., `x[x.length++] = y[i];`)
3. Using a custom loop with array methods like `splice()` or `unshift()`

These alternatives may offer different performance profiles compared to the approaches tested in this benchmark.

Related benchmarks:

concat vs push in various ways (version: 0)

Comparing performance of: concat vs push with rest params vs push in for loop vs push with forEach

Created: 5 years ago by: Guest

Jump to the latest result

concat

push with rest params

push in for loop

push with forEach

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):