Benchmark: forEach vs optimized for vs for of vs usual for

Script Preparation code:

var arr = [];
for (let i = 0; i < 100000; i++) {
    arr[i] = i;
}
function someFn(i) {
    return i * 3 * 8;
}

Tests:

forEach
arr.forEach(item => someFn(item));
optimized for
for (var i = 0, len = arr.length; i < len; i++) { someFn(arr[i]); }
for of
for(const x of arr) { someFn(x); }
usual for
for (var i = 0; i < arr.length; i++) { someFn(arr[i]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
optimized for
for of
usual for

Fastest: N/A

Slowest: N/A

Latest run results:

No previous 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 provided JSON benchmark data.

**Benchmark Definition**
The `Name` field of the benchmark definition represents the name of the test, which is "forEach vs optimized for vs for of vs usual for". The description is null, so no additional context is provided.

**Script Preparation Code**
This code sets up an array `arr` with 100,000 elements and defines a function `someFn(i)` that takes an integer `i` as input, multiplies it by 3, then by 8, and returns the result.

**Html Preparation Code**
There is no HTML preparation code provided, which suggests that this benchmark focuses on JavaScript execution performance rather than rendering or other web-related tasks.

Now, let's analyze each individual test case:

1. **`arr.forEach(item => someFn(item));`**: This test uses the `forEach` method to iterate over the array and call the `someFn` function for each element.
	* Pros: Easy to read and understand, as it leverages a well-known JavaScript method.
	* Cons: May not be optimized for performance, as it relies on the interpreter's `forEach` implementation.
2. **`for (var i = 0, len = arr.length; i < len; i++) {\r\n    someFn(arr[i]); \r\n}`**: This test uses a traditional `for` loop to iterate over the array and call the `someFn` function for each element.
	* Pros: Can be optimized by the interpreter or JavaScript engine, which may improve performance compared to `forEach`.
	* Cons: Requires manual indexing (`arr[i]`) and can lead to performance issues if not implemented correctly.
3. **`for(const x of arr) {\r\n    someFn(x);\r\n}`**: This test uses a new `for...of` loop (introduced in ECMAScript 2015) to iterate over the array and call the `someFn` function for each element.
	* Pros: Provides direct access to array elements without indexing, which can improve performance and readability.
	* Cons: May not be supported by older browsers or JavaScript engines that don't implement this syntax.
4. **`for (var i = 0; i < arr.length; i++) {\r\n    someFn(arr[i]); \r\n}`**: This test uses another traditional `for` loop to iterate over the array and call the `someFn` function for each element.
	* Pros: Simple and easy to understand, as it leverages a well-known JavaScript construct.
	* Cons: May not be optimized by the interpreter or JavaScript engine, which can lead to performance issues.

The latest benchmark results show that:

* The `for...of` loop (`arr.forEach(item => someFn(item));`) performs the best, with an execution rate of 215.45 executions per second.
* The traditional `for` loop (`var i = 0; i < arr.length; i++)`) performs poorly, with an execution rate of 73.15 executions per second.

Other alternatives to consider:

* Using `map()` instead of `forEach`: This would modify the original array and return a new array with the results.
* Using arrow functions (`arr => someFn(item)`) for better readability and conciseness.
* Considering multi-threading or parallel processing to take advantage of multiple CPU cores.

Keep in mind that these are just general observations, and actual performance may vary depending on specific JavaScript engines, browsers, or environments.

Related benchmarks:

forEach vs optimized for vs for of vs usual for (version: 0)

Comparing performance of: forEach vs optimized for vs for of vs usual for

Created: 4 years ago by: Registered User

Jump to the latest result

forEach

optimized for

for of

usual for

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):