Benchmark: JavaScript array copy methods for() vs spread operator

Tests:

for() method copy
let arr1 = [1,2,3,4,5,6,7,8,9,10]; let arr2 = []; for (let i=0; i<arr1.length; i+=1) {arr2.push(arr1[i]);}
spread operator copy
let arr1 = [1,2,3,4,5,6,7,8,9,10]; let arr2 = [...arr1];

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for() method copy
spread operator copy

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36

Browser/OS: Chrome 127 on Windows

View result in a separate tab

Test name	Executions per second
for() method copy	44548492.0 Ops/sec
spread operator copy	92735944.0 Ops/sec

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

LLMs can make mistakes. Check important info.

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

**What is being tested?**

The benchmark measures which method is faster for copying an array: using the `for` loop (`for() method copy`) or the spread operator (`spread operator copy`). The test creates two arrays, `arr1` with a large number of elements (10 in this case), and an empty array `arr2`. It then copies elements from `arr1` to `arr2` using each of the two methods.

**Options compared**

The two options being compared are:

1. **For() method copy**: This involves using a traditional `for` loop to iterate over the elements of `arr1` and push them one by one onto `arr2`.
2. **Spread operator copy**: This uses the spread operator (`...`) to create a new array with all the elements from `arr1`.

**Pros and Cons**

**For() method copy:**

Pros:

* Easy to understand and implement for most developers
* Works well for small arrays or when only a few elements need to be copied

Cons:

* Can be slow due to the overhead of the loop, especially for large arrays
* May not perform well with dynamic array lengths or when dealing with complex data structures

**Spread operator copy:**

Pros:

* Efficient and concise way to create a new array
* Works well with large arrays and can handle complex data structures
* Has become a de facto standard in modern JavaScript development

Cons:

* May be less intuitive for some developers, especially those who are not familiar with the spread operator
* Can be slower than the `for` loop method if the array is very large (although this difference is often negligible)

**Other considerations**

* The test assumes that the arrays are being copied using the `push()` method or similar, which may not always be the case. Other methods of copying elements might have different performance characteristics.
* The test doesn't account for other factors like memory allocation, garbage collection, or concurrent access to the array.
* Different browsers and versions of JavaScript may have different performance characteristics for these two methods.

**Library usage**

There is no library explicitly mentioned in this benchmark. However, if a library were used to create or manipulate arrays (e.g., Lodash), it might affect the performance results.

**Special JS features or syntax**

None of the provided code uses any special JavaScript features or syntax that would be relevant to this benchmark. The focus is on understanding the two array copy methods themselves.

In summary, this benchmark provides a simple and straightforward way to compare the performance of two common array copy methods in JavaScript: using a `for` loop versus the spread operator. By understanding the pros and cons of each approach, developers can make informed decisions about which method to use depending on their specific requirements and constraints.

Related benchmarks:

JavaScript array copy methods for() vs spread operator (version: 0)

The idea is to test which array copy method performs better

Comparing performance of: for() method copy vs spread operator copy

Created: 7 years ago by: Guest

Jump to the latest result

for() method copy

spread operator copy

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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