Benchmark: Array.prototype.concat vs spread operator

Tests:

slice
const params = [1,2,3,4,5,6,7,8,9,0,34,45,45645,645,75,78,868,575,5,235,4,546,567,5,645,645] const copied = params.slice()
spread operator
const params = [1,2,3,4,5,6,7,8,9,0,34,45,45645,645,75,78,868,575,5,235,4,546,567,5,645,645] const copied = [...params]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
spread operator

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

I'll dive into explaining the benchmark and its related concepts.

**Benchmark Overview**

The provided JSON represents a JavaScript microbenchmark created on MeasureThat.net. The benchmark compares two approaches for creating a copy of an array: using the `slice()` method versus the spread operator (`[...]`).

**Options Compared**

Two options are compared:

1. **Array.prototype.slice()**: This method creates a shallow copy of a portion of an array, returning a new array object.
2. **Spread Operator (Array Destructuring)**: This syntax is used to create a new array by spreading the elements of an existing array.

**Pros and Cons**

*   **slice():**
    *   Pros:
        *   Widely supported across different browsers and environments.
        *   Can be more intuitive for developers familiar with this method.
    *   Cons:
        *   Can be slower due to the overhead of creating a new object and iterating over the original array.
        *   Does not support partial copying (i.e., it creates an entirely new array, which can be inefficient if only a portion of the original data is needed).
*   **Spread Operator:**
    *   Pros:
        *   Can be more efficient for large arrays since it avoids creating a new object and iterates over the elements directly.
        *   More modern syntax that is widely adopted in JavaScript.
    *   Cons:
        *   Not supported by older browsers or environments (e.g., Internet Explorer).
        *   May have a higher learning curve due to its more compact syntax.

**Library Usage**

None of the test cases explicitly use any external libraries. Both methods (`slice()` and spread operator`) are part of the standard JavaScript API.

**Special JS Feature or Syntax**

The test case uses the spread operator (`[...]`), which is a relatively new feature introduced in ECMAScript 2015 (ES6). This syntax is designed to create a new array by spreading the elements of an existing array. It's not unique to this benchmark, but its usage here serves to demonstrate its performance compared to other methods.

**Alternatives**

In general, for creating copies of arrays, there are also other approaches:

*   **Array.prototype.slice().slice()**: This is a common pattern where you create the copy using `slice()` and then immediately call `slice()` on it. This approach can be slower than using the spread operator directly.
*   **Array.from()**: Introduced in ECMAScript 2015 (ES6), this method creates a new array from an iterable or an array-like object. It's not specifically designed for creating copies but can be used in certain contexts where performance is critical.

These alternatives might be worth considering depending on the specific requirements and constraints of your project.

In summary, the benchmark provides valuable insights into the relative performance of two common methods for creating array copies: `slice()` versus the spread operator. By understanding the trade-offs between these approaches, developers can make more informed decisions about their code's efficiency and maintainability.

Latest run results:

Run details: (Test run date: 2025 years ago)

User agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36

Browser/OS: Chrome 63 on Windows 8.1

View result in a separate tab

Test name	Executions per second
slice	5783406.5 Ops/sec
spread operator	676873.6 Ops/sec

Related benchmarks:

Array.prototype.concat vs spread operator (version: 0)

Compare the new ES6 spread operator with the traditional concat() method

Comparing performance of: slice vs spread operator

Created: 6 years ago by: Guest

Jump to the latest result

slice

spread operator

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):