Benchmark: Array slice vs for loop vs spread (new Array)

Script Preparation code:

const data = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];

Tests:

slice
const copy = data.slice(0, 5);
push
const copy = new Array(5); for (let i = 0; i < 5; i++) { copy[i] = data[i]; }
Spread
const copy = [...data]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
push
Spread

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 days ago)

User agent: Mozilla/5.0 (Android 15; Mobile; rv:137.0) Gecko/137.0 Firefox/137.0

Browser/OS: Firefox Mobile 137 on Android

View result in a separate tab

Test name	Executions per second
slice	26205038.0 Ops/sec
push	29912088.0 Ops/sec
Spread	8743147.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 2 days ago):

LLMs can make mistakes. Check important info.

The benchmark defined in the provided JSON compares three different methods for creating a copy of a portion of an array in JavaScript: using the `slice` method, a `for` loop with array assignment, and the spread syntax. Each approach has its own strengths and weaknesses. Below is an analysis of each method and other relevant considerations.

### Methods Compared

1. **Array `slice` Method**
   - **Benchmark Definition**: `const copy = data.slice(0, 5);`
   - **Description**: The `slice` method creates a shallow copy of a portion of an array into a new array object selected from start to end (end not included) without modifying the original array.
   - **Pros**:
     - Clean and concise syntax.
     - Native method typically optimized for performance by JavaScript engines.
   - **Cons**:
     - May not be as flexible if you need to modify the copy while also needing to handle complex copying scenarios (e.g., nested arrays).

2. **`for` Loop with Array Assignment**
   - **Benchmark Definition**: 
     ```javascript
     const copy = new Array(5);
     for (let i = 0; i < 5; i++) {
       copy[i] = data[i];
     }
     ```
   - **Description**: This approach manually initializes a new array and populates it in a controlled manner using a loop.
   - **Pros**:
     - Fine-grained control over the copying process.
     - Can be useful for custom logic while copying elements.
   - **Cons**:
     - More verbose and potentially less readable.
     - Can be slower due to the explicit iteration and assignment.
     - Generally less optimized compared to built-in array methods.

3. **Spread Syntax**
   - **Benchmark Definition**: `const copy = [...data];`
   - **Description**: The spread syntax allows the elements of an iterable (like an array) to be included in a new array or in other expressions.
   - **Pros**:
     - Very concise and readable syntax.
     - Easily allows copying of entire arrays.
   - **Cons**:
     - Can be less performant for large arrays compared to optimized methods like `slice`.
     - Not suitable for copying a specific subsection of the array directly without additional logic.

### Performance Results

According to the benchmark results for the `push`, `slice`, and `Spread` methods:
- The `push` method demonstrated the highest execution speed at **29,912,088 executions per second**.
- The `slice` method came in second at **26,205,038 executions per second**.
- The `Spread` syntax had the lowest performance at **8,743,147 executions per second**.

### Alternatives and Considerations

1. **Other Alternatives**:
   - **Using `Array.from()`**: This method creates a new array instance from an array-like or iterable object, potentially acting as an alternative to the spread syntax and `slice`.
     - Example: `const copy = Array.from(data);`
   - **Using `map()`**: If transformations are needed while copying, the `map` method can be used but is mainly for applying functions to elements.
   - **Lodash Library**: For more complex scenarios, libraries like Lodash offer utility functions (e.g., `_.clone`) that provide additional flexibility.

2. **Considerations**:
   - The choice of method may depend on the specific use case, such as the size of the array, readability, and maintainability, as well as performance needs.
   - Benchmarking on different environments (devices and browsers) may yield varying results; hence it's useful to consider this when optimizing code for production.
   - Keep in mind memory implications when dealing with large data sets, particularly if copying involves significant overhead.

In summary, the benchmark compares three ways to copy array portions in JavaScript, each with unique advantages and disadvantages. Performance varies based on implementation and context, while methods like `slice` and loops offer different trade-offs in terms of syntax, readability, and performance.

Related benchmarks:

Array slice vs for loop vs spread (new Array) (version: 1)

Comparing performance of: slice vs push vs Spread

Created: 2 days ago by: Guest

Jump to the latest result

slice

push

Spread

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 2 days ago):