Benchmark: Combining Arrays: Spread vs. Concat 2

Script Preparation code:

var arr1 = [];
for (var j = 0; j < 300; j++) {
  var length = Math.random() * (10 - 2) + 2;
  arr1.push(Math.random().toString(16).substr(2, length));
}
console.log("Init arr1:", arr1);

var arr2 = [];
for (var j = 0; j < 230; j++) {
  var length = Math.random() * (14 - 3) + 3;
  arr2.push(Math.random().toString(16).substr(2, length));
}
console.log("Init arr2:", arr2);

var arr3 = [];
for (var j = 0; j < 80; j++) {
  var length = Math.random() * (8 - 4) + 4;
  arr3.push(Math.random().toString(16).substr(2, length));
}
console.log("Init arr3:", arr3);

var arr4 = [];
for (var j = 0; j < 450; j++) {
  var length = Math.random() * (10 - 2) + 2;
  arr4.push(Math.random().toString(16).substr(2, length));
}
console.log("Init arr4:", arr4);

Tests:

Spread
var bigArraySpread = [...arr1, ...arr2, ...arr3, ...arr4];
Concat
var bigArrayConcat = [].concat(arr1, arr2, arr3, arr4);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread
Concat

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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Let's break down the benchmark and its options.

**Benchmark Definition**

The benchmark is designed to measure the performance difference between two ways of combining arrays: using the spread operator (`...`) and concatenating arrays using the `concat()` method.

**Spread Operator (```var bigArraySpread = [...arr1, ...arr2, ...arr3, ...arr4];``)**

The spread operator is a shorthand way to create a new array by spreading elements from existing arrays. In this benchmark, it's used to combine four arrays (`arr1`, `arr2`, `arr3`, and `arr4`) into a single array.

**Pros of using the Spread Operator:**

*   More concise and readable code
*   Can be faster for large datasets since it avoids creating intermediate arrays

However, there are some potential downsides:

*   May have higher memory overhead due to the creation of new objects (even if they're arrays)
*   Might not work correctly with certain types of data or when dealing with older browsers

**Concat Method (`var bigArrayConcat = [].concat(arr1, arr2, arr3, arr4);``)**

The concatenation method involves creating a new array and appending elements from existing arrays.

Pros of using the Concat Method:

*   Widely supported across different browsers
*   Can be more predictable in terms of performance

However, there are some potential downsides:

*   Less concise code than the spread operator
*   Might result in higher memory overhead due to the creation of intermediate arrays

**Other Considerations:**

*   In JavaScript, when you use the spread operator, it creates a new object (even if it's an array), which can lead to slightly different performance characteristics compared to the concatenation method. This is because objects have additional overhead due to their metadata.
*   When using the spread operator with large datasets, it may be beneficial to consider creating intermediate arrays to avoid excessive memory allocation.

**Library Usage:**

There is no library explicitly used in this benchmark. However, if you were to use libraries like Lodash or Ramda for array operations, they might offer different performance characteristics compared to vanilla JavaScript implementations.

**Special JS Features/Syntax:**

In this benchmark, we're using the spread operator (`...`) and the concatenation method (`concat()`). Both are widely supported across modern browsers but may not work correctly in older browsers. There's no use of special JavaScript features or syntax like ES6 arrow functions, classes, or async/await.

**Other Alternatives:**

If you were to create a similar benchmark for another way of combining arrays, some alternatives could include:

*   Using `Array.prototype.reduce()` to combine arrays
*   Utilizing `Array.prototype.push.apply()` to push elements from one array into another
*   Implementing a custom loop to iterate over and append elements from each array

Keep in mind that the performance characteristics of these alternatives might vary depending on the specific use case, data distribution, and target browser.

Related benchmarks:

Combining Arrays: Spread vs. Concat 2 (version: 0)

Comparing performance of: Spread vs Concat

Created: 4 years ago by: Guest

Jump to the latest result

Spread

Concat

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):