Benchmark: Array concat vs Array.push.apply

Tests:

Regular concat
let arrayA = new Array(500).fill("x",0,500); let arrayB = new Array(500).fill("y",0,500); arrayA = arrayA.concat(arrayB);
Array.push.apply
let arrayA = new Array(500).fill("x",0,500); let arrayB = new Array(500).fill("y",0,500); arrayA.push.apply(arrayA, arrayB);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Regular concat
Array.push.apply

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 10 months ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36

Browser/OS: Chrome 121 on Windows

View result in a separate tab

Test name	Executions per second
Regular concat	172923.7 Ops/sec
Array.push.apply	136226.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**What is being tested?**

The provided benchmark tests two approaches to concatenate arrays: `arrayA.concat(arrayB)` and `arrayA.push.apply(arrayB)`. The test case creates two large arrays (`arrayA` and `arrayB`) filled with 'x' and 'y' characters, respectively, using the `new Array()` constructor and the `fill()` method. The benchmark then measures how long it takes to concatenate these arrays using each of the two approaches.

**Options compared**

The two options being tested are:

1. **`arrayA.concat(arrayB)`**: This is a more traditional way of concatenating arrays in JavaScript. It creates a new array and copies elements from both `arrayA` and `arrayB` into it.
2. **`arrayA.push.apply(arrayB)`**: This approach uses the `push()` method with an array as its argument, effectively applying each element of `arrayB` to `arrayA`.

**Pros and Cons**

*   **`arrayA.concat(arrayB)`**:
    *   Pros: More straightforward and intuitive. Can be easier to read and maintain.
    *   Cons: Creates a new array which can lead to memory allocation overhead, especially for large arrays.
*   **`arrayA.push.apply(arrayB)`**: 
    *   Pros: More efficient in terms of memory usage since it modifies the original array instead of creating a new one. Can be faster than `concat()` due to less overhead from object creation and copying.
    *   Cons: Less readable and more complex, especially for those unfamiliar with `push.apply()`. May not be as performant for very large arrays.

**Library/Function used**

In the provided benchmark, no external libraries are being used. However, if a library or function like Lodash was used instead of using built-in JavaScript functions for concatenation:

*   **`Lodash.concat()`**: Used for concatenating arrays, it's more readable and maintainable than the native `concat()` method.
*   **`Lodash.push.apply()`**: This might be less common as there is no equivalent to Lodash in this case.

**Special JS feature/Syntax**

The provided benchmark uses the following special JavaScript features:

1.  **Template literals (`\r\n`) and multiline strings**: Used for formatting and readability.
2.  **Arrow functions ( implicit, e.g., `let arrayB = new Array(500).fill('y',0,500);` )** : Not explicitly used but still applicable in the context of modern JavaScript.
3.  **ES6+ syntax (`new Array()` constructor)**: Used to create arrays.

Other alternatives for benchmarking JavaScript performance:

1.  **Benchmarking libraries like Benchmark.js**: Specifically designed for measuring performance in JavaScript code, often includes a wide range of test cases and methods to compare different algorithms or approaches.
2.  **Native `performance.now()`** : Simple and straightforward way to measure execution time in JavaScript.
3.  **WebAssembly (WASM)**: For benchmarking CPU-intensive JavaScript code, especially for more low-level performance optimizations.

Overall, these alternatives offer a range of options depending on the specific needs and goals of your benchmarking project.

Related benchmarks:

Array concat vs Array.push.apply (version: 0)

Comparing performance of: Regular concat vs Array.push.apply

Created: 10 months ago by: Guest

Jump to the latest result

Regular concat

Array.push.apply

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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