Benchmark: Combining Arrays: Spread vs. Concat

Script Preparation code:

var arr1 = [];
for (var j; j < 300; j++) {
  arr1.push(Math.random().toString(16).substr(2, 7));
}

var arr2 = [];
for (var j; j < 230; j++) {
  arr2.push(Math.random().toString(16).substr(2, 9));
}

var arr3 = [];
for (var j; j < 80; j++) {
  arr3.push(Math.random().toString(16).substr(2, 8));
}

var arr4 = [];
for (var j; j < 450; j++) {
  arr4.push(Math.random().toString(16).substr(2, 6));
}

console.log("Creating arrays:", arr1, arr2, arr3, 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):

LLMs can make mistakes. Check important info.

**Benchmark Explanation**

The provided benchmark measures the performance difference between two methods of combining arrays in JavaScript: using the spread operator (`...`) and concatenation with `Array.prototype.concat()`. The test cases are designed to simulate real-world scenarios where large arrays need to be combined.

**Options Compared**

There are two main options compared:

1. **Spread Operator**: Using the spread operator (`...`) to combine arrays.
2. **Concatenation**: Using `Array.prototype.concat()` to concatenate arrays.

**Pros and Cons of Each Approach**

* **Spread Operator**:
	+ Pros:
		- More concise and readable syntax.
		- Creates a new array with the elements from the original arrays, which can be more efficient for large datasets.
	+ Cons:
		- May not work as expected if the arrays contain non-array values (e.g., objects or strings).
* **Concatenation**:
	+ Pros:
		- More flexible and forgiving than the spread operator, as it works with non-array values.
	+ Cons:
		- Less concise and less readable syntax.
		- Creates a new array with the elements from the original arrays, which can lead to performance issues for large datasets.

**Library Used**

There is no external library used in this benchmark. The test code only uses built-in JavaScript features.

**Special JS Feature or Syntax**

The benchmark takes advantage of modern JavaScript features, specifically:

* **Destructuring assignment**: Used in the `for` loops to initialize variables.
* **Rest parameter syntax**: Used with `Math.random().toString(16).substr(2, x)` to generate random strings.
* **Arrow functions**: Not used explicitly in this benchmark, but implied by the use of concise syntax.

**Other Considerations**

To provide accurate results, the benchmark:

* Uses a consistent number of iterations for each array (300, 230, 80, and 450).
* Generates random data to simulate real-world scenarios.
* Compares the performance of both methods using the same codebase.

**Alternative Benchmarks**

If you'd like to explore alternative benchmarks or modifications to this one, consider the following:

* **Other array combination methods**: Benchmarking `Array.prototype.push()` and `at()` would provide additional insights into array manipulation performance.
* **Data structure variations**: Comparing the performance of arrays with other data structures (e.g., objects, sets) could reveal interesting results.
* **Edge cases**: Investigating specific edge cases, such as combining very large or empty arrays, could help identify bottlenecks in these methods.

Related benchmarks:

Combining Arrays: Spread vs. Concat (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):