Benchmark: filter vs for performance

Script Preparation code:

var arr = [];
for (var i = 0; i < 12345; i++) {
  arr[i] = i;
}

function someFn(i) {
  return (i > 7890);
}

Tests:

filter
arr.filter(item => someFn(item));
for
const newArr = [] for (var j = 0, len = arr.length; j < len; j++) { const it = arr[i] if (someFn(it)) { newArr.push(it) } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
filter
for

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in the provided JSON benchmark.

**Benchmark Overview**

The benchmark compares two approaches to filtering an array of numbers: using the `filter()` method and using a traditional `for` loop.

**Options Compared**

1. **`arr.filter(item => someFn(item))`**: This is the first option being compared. It uses the `filter()` method, which calls the provided callback function (in this case, `someFn`) for each element in the array and returns an array of elements that pass the test.
2. **`const newArr = []\r\nfor (var j = 0, len = arr.length; j < len; j++) {\r\n  const it = arr[j]\r\n  if (someFn(it)) {\r\n      newArr.push(it)\r\n  }\r\n}`** : This is the second option being compared. It uses a traditional `for` loop to iterate over the array and pushes elements that pass the test into a new array.

**Pros and Cons of Each Approach**

1. **`filter()` method**:
	* Pros:
		+ Concise and expressive code
		+ Efficient, as it only iterates over the filtered elements
		+ Supports arrow functions (in this case, `item => someFn(item)`), which can make the code more readable
	* Cons:
		+ May be slower for very large arrays, due to the overhead of function calls and object lookups
2. **Traditional `for` loop**:
	* Pros:
		+ Can be faster for very large arrays, as it avoids the overhead of function calls and object lookups
		+ Allows for more control over iteration variables and indexing
	* Cons:
		+ More verbose code
		+ Less expressive or concise

**Library**

There is no specific library being used in this benchmark. The `filter()` method is a built-in JavaScript method, and the traditional `for` loop is a standard control structure.

**Special JS Features/Syntax**

None are mentioned. However, it's worth noting that the use of arrow functions (`item => someFn(item)`) is a modern JavaScript feature that can make code more concise and readable.

**Other Alternatives**

If you want to compare other approaches to filtering arrays, here are a few examples:

1. **`forEach()` method**: Instead of `filter()`, you could use the `forEach()` method to iterate over the array.
```javascript
arr.forEach((item) => {
  if (someFn(item)) {
    newArr.push(item);
  }
});
```
2. **`map()` method**: You could also use the `map()` method to filter and transform the array in one step.
```javascript
const newArr = arr.filter(someFn).map((item) => item * 2);
```
3. **`reduce()` method**: Another approach is to use the `reduce()` method to build a new array with filtered elements.
```javascript
const newArr = arr.reduce((acc, item) => {
  if (someFn(item)) {
    acc.push(item);
  }
  return acc;
}, []);
```
These alternatives can provide different trade-offs in terms of performance, readability, and conciseness.

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 16_6 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.6 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 16 on iOS 16.6

View result in a separate tab

Test name	Executions per second
filter	1573.9 Ops/sec
for	780.4 Ops/sec

Related benchmarks:

filter vs for performance (version: 0)

Comparing performance of: filter vs for

Created: one year ago by: Guest

Jump to the latest result

filter

for

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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