Benchmark: for vs for (with length) vs for (reverse with length) vs every vs forEach with small array 2

Script Preparation code:

function generateTestArray() {
	var result = [];

	for (let i = 0; i < 100; ++i) {
		result.push({
			a: i,
			b: i / 2,
			r: 0,
		});
	}

	return result;
}

var array = generateTestArray();

Tests:

for
for (var i = 0; i < array.length; i++) { array[i]; }
for (reverse with length)
var length = array.length; for (var i = length; --i >= 0;) { array[i]; }
some
array.some(function(i) { array[i]; return false; });
every
array.every(function(i) { array[i]; return true; });
forEach
array.forEach(function(i) { array[i]; });
for (with length)
var length = array.length; for (var i = 0; i < length; i++) { let r = array[i]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
for (reverse with length)
some
every
forEach
for (with length)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36

Browser/OS: Chrome 103 on Windows

View result in a separate tab

Test name	Executions per second
for	38439.5 Ops/sec
for (reverse with length)	90957.4 Ops/sec
some	49635.3 Ops/sec
every	50538.2 Ops/sec
forEach	55674.2 Ops/sec
for (with length)	89155.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 5 months ago):

LLMs can make mistakes. Check important info.

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

**Benchmark Overview**

The benchmark compares six different approaches to iterate over an array in JavaScript:

1. `for` loop
2. `for (reverse with length)` loop
3. `every()` method
4. `forEach()` method
5. `for (with length)` loop
6. `some()` method

**What's being tested**

The benchmark measures the performance of each approach in terms of the number of executions per second on a desktop machine running Chrome 103.

**Options compared**

Here's a brief overview of each option:

1. **`for` loop**: A traditional, iterative approach using a variable `i` that increments from 0 to the array length.
2. **`for (reverse with length)` loop**: Similar to the first option, but uses the array length as the upper bound and decrements the counter (`i`) until it reaches 0.
3. **`every()` method**: Returns true if all elements in the array pass the test implemented by the provided function. In this case, each element is accessed and ignored.
4. **`forEach()` method**: Calls a provided function once for each element in the array, passing the element as an argument.
5. **`for (with length)` loop**: Similar to the first option, but uses the `let r = array[i];` syntax to assign the current element to a variable `r`.
6. **`some()` method**: Returns true if at least one element in the array passes the test implemented by the provided function.

**Pros and cons of each approach**

Here's a brief summary:

1. **`for` loop**: Simple and efficient, but can be error-prone due to potential issues with indexing.
	* Pros: Easy to implement and understand
	* Cons: Can lead to off-by-one errors or out-of-bounds access
2. **`for (reverse with length)` loop**: Similar to the first option, but uses a reverse iteration order.
	* Pros: No risk of off-by-one errors, as the counter decrements automatically
	* Cons: Requires manual handling of negative indices
3. **`every()` method**: Efficient and concise, but requires a callback function that returns a boolean value.
	* Pros: Simple and readable, can be used for multiple tests with different conditions
	* Cons: May have performance implications if the test implementation is complex or slow
4. **`forEach()` method**: Easy to use and understand, but may have performance implications due to the need to create an iterator object.
	* Pros: Simple and concise, allows for easy iteration over arrays
	* Cons: May be slower than other options due to the creation of an iterator object
5. **`for (with length)` loop**: Similar to the first option, but uses a different syntax to assign the current element to a variable.
	* Pros: Similar performance characteristics to traditional `for` loops
	* Cons: Less common and less intuitive than traditional `for` loops
6. **`some()` method**: Efficient and concise, but requires a callback function that returns a boolean value.
	* Pros: Simple and readable, can be used for multiple tests with different conditions
	* Cons: May have performance implications if the test implementation is complex or slow

**Other considerations**

1. **Array indexing**: All options use array indexing to access elements. However, the `for` loop and `some()` method are more prone to off-by-one errors due to the lack of bounds checking.
2. **Variable scope**: The `let r = array[i];` syntax in the `for (with length)` loop introduces a new variable scope, which may have performance implications.

**Alternatives**

Other approaches that could be considered for iteration over arrays include:

1. **Using `map()`**, `filter()`, or `reduce()` methods**, which can provide more functionality and flexibility than traditional loops.
2. **Using recursion**, which can be elegant but may lead to stack overflow issues for large arrays.
3. **Using a library like Lodash**, which provides a range of utility functions for array manipulation.

However, the benchmark specifically compares traditional iteration approaches using `for` loops and methods, making it easier to understand and compare their performance characteristics.

Related benchmarks:

for vs for (with length) vs for (reverse with length) vs every vs forEach with small array 2 (version: 0)

Comparing performance of: for vs for (reverse with length) vs some vs every vs forEach vs for (with length)

Created: 2 years ago by: Registered User

Jump to the latest result

for

for (reverse with length)

some

every

forEach

for (with length)

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 5 months ago):