Benchmark: forEach vs reduce vs map vs filter vs for2

Script Preparation code:

var arr = [];
for (var i = 0; i < 12345; i++) {
  arr[i] = i;
}

function someFn(i) {
  return (i * 3 * 8 / 1200 * 0.002 / 40 * 0.2);
}

var sumForEach = 0,
  sumReduce = 0,
  sumMap = 0,
  sumFilter = 0,
  sumFor = 0;

Tests:

forEach
arr.forEach(item => sumForEach += someFn(item));
reduce
sumReduce = arr.reduce((lastValue, item) => { return lastValue += someFn(item); }, 0);
map
arr.map(item => (sumMap += someFn(item)));
filter
arr.filter(item => (sumFilter += someFn(item)));
for
for (var j = 0; j < arr.length; j++) { sumFor += arr[j]; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
reduce
map
filter
for

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model gemma2:9b, generated one year ago):

LLMs can make mistakes. Check important info.

This benchmark compares five different ways to iterate over an array of numbers and perform a calculation on each element in JavaScript:

* **forEach:**  Iterates through each element of the array, executing a provided function for each element. In this case, it calls `someFn` for every item in the array and adds the result to `sumForEach`.
* **reduce:** Reduces the array to a single value by iterating through it and applying a function that accumulates a result. Here, it starts with an initial value of 0 (`lastValue`) and for each element, it adds the result of `someFn` to the current `lastValue`. 
* **map:** Creates a new array by applying a function to each element of the original array. In this test, it applies `someFn` to each element and accumulates the results in `sumMap`, but doesn't use the new array.
* **filter:** Creates a new array containing only the elements for which a provided function returns true.  In this test, it applies `someFn` to each element (though filtering logic isn't used), accumulating the results in `sumFilter`.
* **for loop:** A traditional loop that iterates over the array's indices and accesses each element directly, calculating the sum within the loop.

**Pros & Cons:**

* **forEach:** Simple and readable, good for side effects or when you need to perform actions on each element but don't need a final result.
* **reduce:** Powerful for aggregating data into a single value, often used for calculations that involve accumulating a sum, product, or other value. 
* **map:** Efficient for creating new arrays based on transformations of existing elements, useful when you need to generate a modified version of the original array.
* **filter:** Ideal for selecting specific elements from an array based on a condition, simplifying data manipulation and analysis.
* **for loop:**  Provides fine-grained control over iteration, allowing direct access to indices and potential for optimization in some cases.

**Considerations:**

* The performance differences observed in the benchmark results might be influenced by factors like JavaScript engine optimizations, the specific calculations performed within `someFn`, and other code executing concurrently on the system.
* Choosing the best approach often depends on the specific use case and desired outcome.  Consider the nature of the data manipulation, whether you need a final result, the complexity of the operations, and readability for maintainability.

**Alternatives:**

While not explicitly tested in this benchmark, other JavaScript paradigms like asynchronous programming with Promises or async/await could be used to handle array processing differently, especially when dealing with large datasets or I/O-bound operations.

Related benchmarks:

forEach vs reduce vs map vs filter vs for2 (version: 0)

Comparing performance of: forEach vs reduce vs map vs filter vs for

Created: 6 years ago by: Guest

Jump to the latest result

forEach

reduce

map

filter

for

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model gemma2:9b, generated one year ago):