Benchmark: for vs foreach vs for..of vs for..of over entries vs for in

Script Preparation code:

var array = Array.from({length: 100});
var t;

Tests:

for
for (let i = 0; i < array.length; i++) { t = array[i]; }
foreach
array.forEach(function(v, i) { t = v; });
for..of
for (var v of array) { t = v; }
for..of over entries
for (var [i, v] of array.entries()) { t = v; }
for..in
for (var k in array) { t = array[k]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for
foreach
for..of
for..of over entries
for..in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 12 days ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:128.0) Gecko/20100101 Firefox/128.0

Browser/OS: Firefox 128 on Linux

View result in a separate tab

Test name	Executions per second
for	9486539.0 Ops/sec
foreach	1078784.2 Ops/sec
for..of	1989419.2 Ops/sec
for..of over entries	665126.1 Ops/sec
for..in	426679.7 Ops/sec

Autogenerated LLM Summary (model gemma2:9b, generated 6 months ago):

LLMs can make mistakes. Check important info.

This benchmark on MeasureThat.net compares the performance of different ways to iterate over an array in JavaScript.

**Options Compared:**

* **`for` loop:** The classic way to loop, using an index (`i`) to access each element.
* **`forEach()` method:**  A higher-order function that iterates over each element and calls a provided callback function.
* **`for...of` loop:** A modern syntax for iterating directly over the values in an iterable (like an array). 
* **`for...of` over `entries()`:** This loops over the key-value pairs of the array using `entries()`.  While useful, it's not the most common way to iterate over values alone.
* **`for...in` loop:** Loops over the enumerable properties (keys) of an object. While it can work on arrays, it's generally less efficient and meant for objects.

**Pros and Cons:**

* **`for` loop:**  Can be very performant if you need to access element indices, but verbose.
* **`forEach()`:** Concise and readable, good for simple operations. Might have a slight performance overhead compared to `for...of`. 
* **`for...of`:** Most concise and often the fastest for simple iteration over values.
* **`for...of` over `entries()`:** Useful if you need both index/value pairs, but adds extra processing.

**Other Considerations:**

*  The benchmark results can vary based on factors like JavaScript engine optimization, browser versions, hardware, and even network conditions. Always interpret benchmarks with caution.
* **Choosing the best approach:** Consider:
    * Do you need the element's index? (`for` loop or `forEach`)
    * Is simplicity most important? (`for...of`) 
    * Are you working with objects or arrays? (Avoid `for...in` for arrays)

Let me know if you have any more questions about JavaScript loops or performance testing!

Related benchmarks:

for vs foreach vs for..of vs for..of over entries vs for in (version: 0)

Compare loop performance

Comparing performance of: for vs foreach vs for..of vs for..of over entries vs for..in

Created: one year ago by: Guest

Jump to the latest result

for

foreach

for..of

for..of over entries

for..in

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gemma2:9b, generated 6 months ago):