Benchmark: spread vs idx - MeasureThat.net

Script Preparation code:

var randomArray = Array.from({
        length: 100
    }, () =>
    Math.floor(Math.random() * 100)
);

Tests:

spread
randomArray.reduce((acc, cur) => { return [...acc, cur]; }, []);
idx
randomArray.reduce((acc, cur, idx) => { acc[idx] = cur; return acc; }, []);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
spread
idx

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.2.1 Safari/605.1.15

Browser/OS: Safari 17 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
spread	55629.9 Ops/sec
idx	1407759.9 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 benchmark and explain what is being tested.

The benchmark compares two approaches to modifying an array: using the spread operator (`...`) and accessing indices directly (`idx`).

**Approach 1: Using the Spread Operator**

In this approach, the `randomArray.reduce()` method creates a new array by spreading the elements of the accumulator (`acc`) into a new array. The purpose of this operation is to create a copy of the original array with all its elements.

The pros of using the spread operator are:

* It's concise and readable.
* It avoids modifying the original array, which can be beneficial in certain scenarios.
* It's widely supported across modern browsers and JavaScript engines.

However, there are some potential cons:

* Creating a new array can be computationally expensive for large datasets.
* The spread operator may not perform as well as direct indexing if the array is already sparse or has a lot of holes.

**Approach 2: Accessing Indices Directly**

In this approach, the `randomArray.reduce()` method modifies the accumulator (`acc`) by assigning each element to its corresponding index. The purpose of this operation is to create a new array with the same elements as the original array.

The pros of accessing indices directly are:

* It's more efficient than using the spread operator for large datasets.
* It avoids creating a new array, which can be beneficial in terms of memory usage.

However, there are some potential cons:

* The code is less concise and may look less readable to some developers.
* This approach requires manual index calculation, which can lead to errors if not implemented correctly.

**Library Usage**

Neither of the benchmark's test cases uses any external libraries. However, `Array.from()` is used in the script preparation code to create a random array, which is a modern JavaScript API introduced in ECMAScript 2015 (ES6).

**Special JavaScript Features or Syntax**

There are no special JavaScript features or syntaxes used in these benchmark test cases.

**Other Alternatives**

If you wanted to implement this benchmark using a different approach, some alternatives could be:

* Using `Array.prototype.slice()` instead of the spread operator.
* Using a custom implementation of array concatenation.
* Using a library like Lodash that provides efficient array manipulation functions.
* Using a framework like React or Angular that optimizes array updates for performance.

Keep in mind that these alternatives might not provide the same level of conciseness, readability, and performance as the original benchmark test cases.

Related benchmarks:

spread vs idx (version: 0)

Comparing performance of: spread vs idx

Created: 2 years ago by: Guest

Jump to the latest result

spread

idx

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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