Benchmark: Spread Push VS Concat Reassign

Script Preparation code:

var data = [
  1, 2, 3, 4,
  [1, 2, 3, 4],
  5, 6, 7, 8,
  [1, 2, 3, 4]
];

Tests:

Spread Push
(function fn(items){ var result = []; items.forEach(item => { if(item.pop) { result.push(...fn(item)); } else { result.push(item); } }); return result; })(data);
Concat Reassign
(function fn(items){ var result = []; items.forEach(item => { if(item.pop) { result = result.concat(fn(item)); } else { result.push(item); } }); return result; })(data);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Spread Push
Concat Reassign

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested.

**Benchmark Definition**

The benchmark is designed to compare two approaches:

1. **Spread Push**: This approach uses the spread operator (`...`) to create a new array by spreading elements from an existing array.
2. **Concat Reassign**: This approach uses the `concat()` method to concatenate arrays and reassign the result.

**Script Preparation Code**

The script preparation code provides the data for the benchmark:
```javascript
var data = [
  1, 2, 3, 4,
  [1, 2, 3, 4],
  5, 6, 7, 8,
  [1, 2, 3, 4]
];
```
This data consists of an array with four elements: two numbers and two arrays.

**Html Preparation Code**

There is no HTML preparation code provided, which means that the benchmark focuses solely on JavaScript execution performance.

**Individual Test Cases**

The benchmark defines two individual test cases:

1. **Spread Push**
```javascript
(function fn(items){
  var result = [];
  items.forEach(item => {
    if(item.pop) {
      result.push(...fn(item));
    } else {
      result.push(item);
    }
  });
  return result;
})(data);
```
This implementation uses the spread operator to create a new array by spreading elements from each inner array.

2. **Concat Reassign**
```javascript
(function fn(items){
  var result = [];
  items.forEach(item => {
    if(item.pop) {
      result = result.concat(fn(item));
    } else {
      result.push(item);
    }
  });
  return result;
})(data);
```
This implementation uses the `concat()` method to concatenate arrays and reassign the result.

**Library**

There is no explicit library mentioned in the benchmark definition or test cases. However, it's likely that the benchmark is using a built-in JavaScript function or method (e.g., `forEach()`, `push()`, `concat()`) without referencing any external libraries.

**Special JS Feature/Syntax**

The benchmark uses the following special feature:

* **Spread Operator (`...`)**: This operator was introduced in ECMAScript 2015 (ES6) and allows creating a new array by spreading elements from an existing array.
* **Arrow Functions (`() => {...}`)**: These functions were also introduced in ES6 and provide a concise way to define small, single-expression functions.

**Pros and Cons**

Here are some pros and cons of each approach:

1. **Spread Push**
	* Pros:
		+ More concise and expressive code
		+ Faster execution due to the use of `...` operator
	* Cons:
		+ May not be supported in older browsers or environments that don't support ES6 features
2. **Concat Reassign**
	* Pros:
		+ More widely supported, as it uses built-in methods (`concat()`)
		+ Easier to read and understand for those familiar with traditional array concatenation
	* Cons:
		+ Less concise code compared to Spread Push
		+ May be slower due to the reassignment of `result` variable

**Other Alternatives**

Some alternative approaches could be considered:

1. **Using a temporary array**: Create a new, temporary array and push elements into it using `push()`, then return the temporary array.
2. **Using `Array.prototype.reduce()`**: Use `reduce()` to iterate over the inner arrays and accumulate the results in a single array.

However, these alternatives may not be as concise or efficient as the Spread Push and Concat Reassign approaches used in the benchmark.

Latest run results:

Run details: (Test run date: 7 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.95 Safari/537.36

Browser/OS: Chrome 55 on Mac OS X 10.11.6

View result in a separate tab

Test name	Executions per second
Spread Push	190417.7 Ops/sec
Concat Reassign	310196.7 Ops/sec

Related benchmarks:

Spread Push VS Concat Reassign (version: 0)

Comparing performance of: Spread Push vs Concat Reassign

Created: 8 years ago by: Guest

Jump to the latest result

Spread Push

Concat Reassign

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):