Benchmark: for vs foreach vs some

Script Preparation code:

var array = new Array(100);
for(var i = 0; i < array.length; i++) {
	array[i] = Math.random();
}

Tests:

for..in
for (var i in array) { array[i]; }
foreach
array.forEach(function(item, index) { return item; });
some
array.some(function(item, index) { return item === array[index]; });
for
for (var i = 0; i < array.length; i++) { array[i]; }
for with predefined size
var size = array.length for (var i = 0; i < size; i++) { array[i]; }
while
while((a=array.pop()) !== undefined){ //do your stuff }
every
array.every(function(item, index) { return item === array[index]; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for..in
foreach
some
for
for with predefined size
while
every

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/107.0.0.0 Safari/537.36 Edg/107.0.1418.42

Browser/OS: Chrome 107 on Windows

View result in a separate tab

Test name	Executions per second
for..in	113247.7 Ops/sec
foreach	10574585.0 Ops/sec
some	7757586.0 Ops/sec
for	81638.8 Ops/sec
for with predefined size	162947.8 Ops/sec
while	3017210.2 Ops/sec
every	15027196.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Measuring the performance of different JavaScript loops is crucial for optimizing code and improving application performance.

**What is being tested?**

The provided JSON benchmark definition tests the performance of various JavaScript loop constructs:

1. `for` loop: Iterates over an array using a traditional `for` loop with an incrementing index.
2. `foreach` loop (also known as `for...of`): Iterates over an array using the `forEach()` method, which calls a provided callback function for each element in the array.
3. `some` loop: Iterates over an array and returns `true` if at least one element meets a certain condition. In this case, it checks if each element is equal to its index in the array.
4. `for..in` loop (not strictly a traditional loop): Iterates over an object using the `for...in` statement, which iterates over the object's enumerable properties.

**Options compared**

The benchmark compares the performance of these different loop constructs on the same array of 100 elements.

**Pros and cons of each approach:**

1. **Traditional `for` loop**: Pros - Simple to implement, easy to understand, and widely supported. Cons - Can be slower than other approaches due to the overhead of indexing.
2. **Foreach loop (`for...of`)**: Pros - Convenient, readable, and efficient. Cons - May have performance overhead due to the creation of a new scope for each iteration.
3. **Some loop**: Pros - Short and concise, easy to implement. Cons - Can be slower than traditional loops due to the overhead of checking the condition on each element.
4. **For..in loop**: Pros - Can iterate over objects, including arrays as objects with numerical indices. Cons - Not strictly a traditional loop, can lead to unexpected behavior if not used carefully.

**Other considerations:**

* In modern JavaScript engines, `for...of` loops are generally considered the most efficient and convenient way to iterate over arrays.
* The `some` loop is useful when you need to check if at least one element in an array meets a condition. However, it may be slower than traditional loops due to the overhead of checking each element.
* The `for..in` loop can be misleading for array iteration, as it iterates over the object's properties (including numerical indices). Use with caution when iterating over arrays.

**Alternatives:**

1. **Loop unrolling**: Some loops can be optimized by unrolling them, which involves adding extra iterations to reduce the overhead of conditional statements.
2. **Cache-friendly data structures**: Using cache-friendly data structures, such as arrays with a fixed length or objects with numerical indices, can improve performance for certain loop constructs.

Keep in mind that these alternatives may require additional optimization and testing to ensure they provide a noticeable performance boost.

Related benchmarks:

for vs foreach vs some (version: 0)

Compare loop performance

Comparing performance of: for..in vs foreach vs some vs for vs for with predefined size vs while vs every

Created: 7 years ago by: Guest

Jump to the latest result

for..in

foreach

some

for

for with predefined size

while

every

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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