Benchmark: for loop vs foreach vs map (obj mutation)

Script Preparation code:

   var arr = [];
   for (var i = 0; i < 1000; i++) {
     arr[i] = { x0: 0, x1: i, y0: 0, y1: i, dx: 0, dy:0 };
   }

   var len = arr.length;

Tests:

for loop
for (var i = 0; i < len; i++) { arr[i].dx = arr[i].x1 - arr[i].x0; arr[i].dy = arr[i].y1 - arr[i].y0; arr[i].x0 = arr[i].dx - arr[i].dx / 2; arr[i].x1 = arr[i].dx + arr[i].dx / 2; arr[i].y0 = arr[i].dy - arr[i].dy / 2; arr[i].y1 = arr[i].dy + arr[i].dy / 2; arr[i].dx = arr[i].x1 - arr[i].x0; arr[i].dy = arr[i].y1 - arr[i].y0; }
forEach
arr.forEach(function (it){ it.dx = it.x1 - it.x0; it.dy = it.y1 - it.y0; it.x0 = it.dx - it.dx / 2; it.x1 = it.dx + it.dx / 2; it.y0 = it.dy - it.dy / 2; it.y1 = it.dy + it.dy / 2; it.dx = it.x1 - it.x0; it.dy = it.y1 - it.y0; })
map (same object)
var newArr = arr.map(it => { it.dx = it.x1 - it.x0; it.dy = it.y1 - it.y0; it.x0 = it.dx - it.dx / 2; it.x1 = it.dx + it.dx / 2; it.y0 = it.dy - it.dy / 2; it.y1 = it.dy + it.dy / 2; it.dx = it.x1 - it.x0; it.dy = it.y1 - it.y0; return it; })
map (new obj)
var newArr = arr.map(it => { return { dx: it.x1 - it.x0, dy: it.y1 - it.y0, x0: it.dx - it.dx / 2, x1: it.dx + it.dx / 2, y0: it.dy - it.dy / 2, y1: it.dy + it.dy / 2, dx: it.x1 - it.x0, dy: it.y1 - it.y0, }; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for loop
forEach
map (same object)
map (new obj)

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 dive into the provided benchmark.

**Benchmark Definition**

The benchmark tests three different approaches to perform calculations on an array of objects: for loops, foreach loops, and using the map() method with two variations: assigning the result back to the same object or creating a new object.

**Options Compared**

1. **For Loop**: A traditional loop that iterates over each element in the array.
2. **Foreach Loop**: A loop that iterates over each element in the array, but uses an iterator function (function() {}) to access each element.
3. **Map Method with Same Object**: The map() method is used to create a new array with the results of applying a provided function to each element in the original array. The returned object is assigned back to the same object as before using the dot notation (.).
4. **Map Method with New Object**: Similar to the previous option, but the map() method returns a new object instead of assigning it back to the same object.

**Pros and Cons**

1. **For Loop**:
	* Pros: Can be more efficient for small arrays or when working with objects that have many properties.
	* Cons: Can be slower for large arrays due to the overhead of creating a loop variable and updating its value on each iteration.
2. **Foreach Loop**:
	* Pros: Similar to traditional loops, but with less boilerplate code required.
	* Cons: May not perform as well as for loops for very large arrays or complex calculations.
3. **Map Method with Same Object**:
	* Pros: Can be more memory-efficient than creating a new object on each iteration.
	* Cons: Assigning the result back to the same object can lead to unexpected behavior if the function modifies the original object's properties.
4. **Map Method with New Object**:
	* Pros: Creates a new object for each iteration, which can be more predictable and avoid potential issues with modifying the original object.
	* Cons: Can be less efficient than other options due to the overhead of creating a new object on each iteration.

**Library/Function Used**

The map() method is used in all three variations. The foreach loop uses an iterator function (function() {}) to access each element, which is not explicitly defined but is automatically provided by the JavaScript engine.

**Special JS Feature/Syntax**

None mentioned, but the use of dot notation for property assignment (.it.dx) and object creation ({ dx: ... }) are standard JavaScript syntax.

**Alternative Approaches**

Other approaches that could be used to compare include:

1. **Lodash functions**: Similar to map(), but provides more functionality and options (e.g., _.map(), _.each(), etc.).
2. **Array.prototype.reduce()**: A method that reduces an array of values to a single output value, which can be compared with the other options.
3. **Closures**: Using closures to create functions that iterate over the array can provide more flexibility and control.

These alternatives could add additional complexity and overhead to the benchmark, but might also provide interesting insights into different aspects of performance optimization in JavaScript.

Related benchmarks:

for loop vs foreach vs map (obj mutation) (version: 0)

Comparing performance of: for loop vs forEach vs map (same object) vs map (new obj)

Created: 5 years ago by: Guest

Jump to the latest result

for loop

forEach

map (same object)

map (new obj)

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):