Benchmark: desctructuring array keys vs access via index

Script Preparation code:

const data = Array.from({length: 1_000_000}, () => [
    Math.random(),
    Math.random(),
    Math.random(),
]);

Tests:

Array Destructuring
let sum1 = 0; for (let i = 0; i < data.length; i++) { const [a, b, c] = data[i]; sum1 += a + b + c; }
Index Access
let sum2 = 0; for (let i = 0; i < data.length; i++) { const arr = data[i]; sum2 += arr[0] + arr[1] + arr[2]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Array Destructuring
Index Access

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; rv:137.0) Gecko/20100101 Firefox/137.0

Browser/OS: Firefox 137 on Windows

View result in a separate tab

Test name	Executions per second
Array Destructuring	146.2 Ops/sec
Index Access	226.1 Ops/sec

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

LLMs can make mistakes. Check important info.

The benchmark "destructuring array keys vs access via index" evaluates two different methods for accessing values from an array of arrays in JavaScript. This comparison helps to understand the performance differences between using array destructuring and accessing array elements via index.

### Options Compared

1. **Array Destructuring:**
   - **Code:** 
     ```javascript
     const [a, b, c] = data[i];
     ```
   - In this approach, each element of the inner array (which contains three randomly generated numbers) is unpacked into separate variables `a`, `b`, and `c`.
   - **Pros:**
     - Cleaner and more readable syntax, which is easier for developers to understand at a glance.
     - Reduces the need for repeated array indexing, which can make the code less error-prone.
   - **Cons:**
     - Possible performance overhead due to the additional syntax and the destructuring operation, which could be less optimized in some JavaScript engines.
     - Slightly more initial memory allocation might occur because of the need to create new variables for each destructured element.

2. **Index Access:**
   - **Code:**
     ```javascript
     const arr = data[i];
     sum2 += arr[0] + arr[1] + arr[2];
     ```
   - Here, the code accesses each element of the inner array directly using its index. 
   - **Pros:**
     - Potentially better performance in some scenarios since it involves simple index lookups without the additional overhead of destructuring.
     - Often more performance-optimized in JavaScript engines.
   - **Cons:**
     - Readability may decrease, especially with longer arrays or more complex data structures, as it can lead to more repetitive and error-prone code.
     - Requires the coder to ensure the correct indices are used, which can be error-prone.

### Benchmark Results Analysis

From the benchmark results:
- **Index Access** executed **226.06 Executions Per Second**, while **Array Destructuring** executed **146.23 Executions Per Second**. This indicates that accessing elements via index is significantly faster than using destructuring in this case.

### Libraries and Features

This benchmark does not utilize any external libraries; it strictly examines native JavaScript capabilities. The focus remains on analyzing the performance of two built-in syntax features: array destructuring and array indexing.

### Other Considerations and Alternatives

- **Readability vs Performance:** Depending on the context, developers might prioritize clarity and maintainability over raw performance. In applications where performance is critical, the index access method may be preferable.
  
- **TypeScript Considerations:** If using TypeScript, destructuring can provide type inference which could be advantageous in larger codebases.

- **Alternatives:** 
   - **ForEach and Reduce:** For summing values, alternative methods like `.forEach()` or `.reduce()` may also be considered. However, they might introduce performance overhead due to function calls.
   - **Typed Arrays:** For scenarios where performance is crucial (like numerical computations), using typed arrays (like `Float32Array`) might yield better performance.

In summary, this benchmark serves as an excellent case study for developers aiming to understand trade-offs between code clarity and execution performance in JavaScript array manipulation techniques.

Related benchmarks:

desctructuring array keys vs access via index (version: 1)

Comparing performance of: Array Destructuring vs Index Access

Created: one year ago by: Registered User

Jump to the latest result

Array Destructuring

Index Access

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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