Let's dive into the world of JavaScript microbenchmarks!

Benchmark Overview

The provided JSON represents a benchmark test on MeasureThat.net, which compares three approaches to concatenate arrays in JavaScript:

1. The traditional concat() method
2. The new ES6 spread operator (...)

These approaches are compared using three individual test cases.

Test Case 1: Array concat

const arr = [1, 2, 3];
const res = arr.concat(4);

This test case uses the traditional concat() method to concatenate an array [1, 2, 3] with a new element 4. The resulting concatenated array is stored in res.

Pros and Cons of Array concat

• Pros:
  • Wide browser support (has been around for decades)
  • Simple and intuitive syntax
• Cons:
  • Can be slower than other approaches due to its method call overhead

Test Case 2: Spread operator (appended)

const arr = [1, 2, 3];
const res = [...arr, 4];

This test case uses the spread operator (...) to concatenate an array [1, 2, 3] with a new element 4. The resulting concatenated array is stored in res.

Pros and Cons of Spread operator (appended)

• Pros:
  • Faster than traditional concat() due to its syntax optimization
  • More concise and modern syntax
• Cons:
  • Requires ES6+ support (not supported in older browsers)
  • May not work as expected if the spread expression is used incorrectly

Test Case 3: Spread operator (prepended)

const arr = [1, 2, 3];
const res = [0, ...arr];

This test case uses the spread operator (...) to prepend an element 0 to an array [1, 2, 3]. The resulting prepended array is stored in res.

Pros and Cons of Spread operator (prepended)

• Pros:
  • Similar benefits as the appended variant (faster and more concise syntax)
  • Works with any type of spread expression
• Cons:
  • Less intuitive syntax than traditional concat() or appending variant

Library Used

In this benchmark, no specific JavaScript library is used. The test cases only use built-in JavaScript features.

Special JS Features/Syntax

The ES6 spread operator (...) is a special feature introduced in ECMAScript 2015 (ES6). It allows for concise and expressive array concatenation and manipulation. However, it requires modern browser support and may not work as expected in older browsers or environments with limited JavaScript capabilities.

Other Alternatives

In addition to the traditional concat() method and spread operator approaches, there are other ways to concatenate arrays in JavaScript:

• Using Array.prototype.push(): arr.push(4)
• Using a loop: for (let i = 0; i < arr.length; i++) { arr[i] = 4 }
• Using the Array.from() method: const res = Array.from(arr, () => 4)