Benchmark: arr.push vs re-set

HTML Preparation code:

<!--your preparation HTML code goes here-->

Script Preparation code:

const arr = new Array(10);

Tests:

arr push
const foo = []; foo.push(...arr);
re-define
let foo = []; foo = arr;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
arr push
re-define

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36

Browser/OS: Chrome 135 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
arr push	31937368.0 Ops/sec
re-define	175040224.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

LLMs can make mistakes. Check important info.

The benchmark compares two different approaches for adding elements from one array to another in JavaScript: using the `Array.prototype.push` method with the spread operator versus directly reassigning a new array to a variable. Here's a more detailed breakdown of each approach, their pros and cons, and other relevant considerations.

### Benchmark Overview

1. **Benchmark Name**: "arr.push vs re-set"
2. **Preparation Code**: Initializes an array `arr` with 10 elements.
3. **Test Cases**:
   - **Test Case 1: "arr push"**
     - **Code**: `const foo = []; foo.push(...arr);`
     - **Description**: This method creates an empty array called `foo` and uses the `push` method combined with the spread operator `...` to add all elements from the `arr` array to the `foo` array.
   
   - **Test Case 2: "re-define"**
     - **Code**: `let foo = []; foo = arr;`
     - **Description**: This method creates an empty array `foo` and then reassigns `foo` to reference the `arr` array directly.

### Performance Results
The results of the latest benchmark run showed the following executions per second for each method:

- **re-define**: 175,040,224.0 executions per second
- **arr push**: 31,937,368.0 executions per second

### Comparison of Options

#### 1. arr.push(...arr)
- **Pros**:
  - Generates a new array (`foo`) containing a copy of the elements.*
  - Preserves the integrity of the original `arr` (if changes to `foo` do not affect `arr`).
- **Cons**:
  - Higher computational cost due to the use of the spread operator and the need to build a new array, which may not be optimal for larger arrays.
  
#### 2. foo = arr
- **Pros**:
  - Efficient as it simply makes `foo` reference the same object in memory as `arr`; fewer operations lead to higher performance.
  - No memory overhead of duplicating the elements.
  
- **Cons**:
  - Changes to `foo` will directly affect `arr`, as both references point to the same array in memory (if the intention is to have `foo` independent of `arr`, this wouldn't be desired).

### Considerations
- **Memory Management**: If you want to create copies of arrays without affecting the originals, using `push` with the spread operator is the appropriate method, though it comes with a larger memory footprint for the new array. If memory performance and speed are critical, especially with large datasets, the redefinition approach may be more efficient but at the cost of shared state between `foo` and `arr`.
  
- **Use Cases**: Choosing between these methods depends on the specific requirements of the project. For instance, if deep control over array manipulation is needed without affecting the source array, `arr.push(...)` is the more suitable choice. Conversely, if you are working with data that does not require such isolation, the re-define approach is more performant.

### Alternatives
- **Array.concat()**: Instead of directly using `push` for array concatenation, one could use `arr.concat(foo)`, though it is generally less performant than re-assigning or using the spread operator.
- **ForEach or Loops**: Manual iteration with loops can also be a possibility, but generally would be less optimal for large data sets compared to the approaches examined.

Both methods serve different purposes based on array handling requirements, and understanding the pros and cons helps engineers make informed decisions based on the context of use.

Related benchmarks:

arr.push vs re-set (version: 1)

Comparing performance of: arr push vs re-define

Created: one year ago by: Guest

Jump to the latest result

arr push

re-define

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):