Benchmark: JS Concat vs Spread

Script Preparation code:

var sampleArr1 = new Array(50000).fill('a')
var sampleArr2 = new Array(50000).fill('b')

Tests:

Concat
var resultArr = sampleArr1.concat(sampleArr2)
Spread
var resultArr = [...sampleArr1, ...sampleArr2]

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Concat
Spread

Fastest: N/A

Slowest: N/A

Latest run results:

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

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**Overview**

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks, comparing different approaches and libraries to determine their performance.

The provided benchmark tests two approaches for concatenating arrays in JavaScript:

1. Using the `concat()` method
2. Using the spread operator (`...`)

Let's break down each approach, its pros and cons, and other considerations.

**Approach 1: Concat() Method**

The `concat()` method is a built-in JavaScript method that appends one or more arrays to another array. It returns a new array containing all elements from both arrays.

```javascript
var sampleArr1 = new Array(50000).fill('a');
var sampleArr2 = new Array(50000).fill('b');
var resultArr = sampleArr1.concat(sampleArr2);
```

Pros:

* Easy to read and understand
* Works in most browsers

Cons:

* Creates a new array, which can be memory-intensive for large arrays
* May lead to slower performance compared to other approaches

**Approach 2: Spread Operator (`...`)**

The spread operator is a new feature introduced in ECMAScript 2015. It allows you to expand an array into multiple arguments.

```javascript
var sampleArr1 = [...new Array(50000).fill('a')];
var sampleArr2 = [...new Array(50000).fill('b')];
var resultArr = [...sampleArr1, ...sampleArr2];
```

Pros:

* More memory-efficient compared to `concat()`
* Can lead to better performance due to array reuse

Cons:

* Requires support for the spread operator (which is enabled in most modern browsers)
* May be less readable for developers unfamiliar with this syntax

**Other Considerations**

When choosing between these two approaches, consider the following factors:

* **Memory constraints**: If you're working with very large arrays, using the spread operator might be more memory-efficient.
* **Readability and maintainability**: For smaller arrays or simpler codebases, the `concat()` method might be easier to understand and read.
* **Performance**: In most cases, the spread operator will lead to better performance due to array reuse.

**Library Usage**

There is no external library used in this benchmark. The only libraries used are:

* `Array` (which is a built-in JavaScript object)

**Special JS Features/Syntax**

The benchmark uses the spread operator (`...`) which is a special feature introduced in ECMAScript 2015. This feature allows expanding arrays into multiple arguments, making it more concise and expressive.

In summary, MeasureThat.net provides a useful platform for comparing different approaches to array concatenation in JavaScript. Understanding the pros and cons of each approach can help developers make informed decisions about their code's performance and memory usage.

Related benchmarks:

JS Concat vs Spread (version: 0)

Comparing performance of: Concat vs Spread

Created: 4 years ago by: Guest

Jump to the latest result

Concat

Spread

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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