Benchmark: For in vs Object.keys.forEach FixedForYaRetard

Script Preparation code:

var obj = new Object()
var keys = (new Array(10000)).fill(0).map((x, i) => { return i + 1 })
keys.forEach((x) => { obj['prop' + x] = x })

Tests:

For In
var sum = 0 for (var key in obj) { sum++ }
Object keys forEach
var sum = 0 Object.keys(obj).forEach(val => { sum++ })

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For In
Object keys forEach

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the benchmark and its test cases.

**Benchmark Definition:**
The benchmark is designed to compare two approaches for iterating over an object in JavaScript: `for...in` loop and `Object.keys()` with `forEach()` method.

**Script Preparation Code:**
The script creates a new object `obj` with 10,000 properties (using the `fill()` method and then mapping a function to create each property). The script then sets up an empty variable `sum`.

**Html Preparation Code:**
There is no HTML preparation code provided for this benchmark.

**Individual Test Cases:**

1. **For In:**
	* Benchmark Definition:
```javascript
var sum = 0;
for (var key in obj) {
  sum++;
}
```
	* This approach iterates over the object's properties using a `for...in` loop, which includes inherited properties.
2. **Object keys forEach:**
	* Benchmark Definition:
```javascript
var sum = 0;
Object.keys(obj).forEach(val => {
  sum++;
});
```
	* This approach uses the `Object.keys()` method to get an array of the object's own enumerable property names, and then iterates over that array using the `forEach()` method.

**Pros and Cons:**

1. **For In:**
	* Pros:
		+ May be faster for objects with many properties (due to branch prediction)
		+ Can handle inherited properties
	* Cons:
		+ Iterates over all properties, including inherited ones, which can lead to slower performance for large objects
		+ Less predictable behavior due to potential side effects from iterating over properties in an unexpected order
2. **Object keys forEach:**
	* Pros:
		+ More predictable and safer than `for...in` (as it doesn't iterate over inherited properties)
		+ Typically faster than `for...in` for modern JavaScript engines (due to caching and optimization)
	* Cons:
		+ May be slower for small objects or arrays (due to the overhead of creating an array and iterating over it)

**Library:**
There is no library used in this benchmark.

**Special JS feature/syntax:**
None mentioned.

**Other Considerations:**

1. **Inheritance:** The `for...in` loop iterates over all properties, including inherited ones, which can lead to slower performance for large objects.
2. **Caching:** Modern JavaScript engines use caching mechanisms to optimize iteration over arrays and objects. This means that `Object.keys()` with `forEach()` may benefit from caching in some cases.

**Alternatives:**
Other alternatives for iterating over an object in JavaScript include:

1. Using a simple `for` loop with indexing (e.g., `for (var key = 0; key < obj.length; key++)`)
2. Using the `entries()` method to iterate over both keys and values simultaneously (e.g., `for (const [key, value] of Object.entries(obj))`)
3. Using a library like Lodash to provide utility functions for iterating over objects.

Note that these alternatives may have different performance characteristics compared to the original benchmark.

Related benchmarks:

For in vs Object.keys.forEach FixedForYaRetard (version: 0)

Comparing performance of: For In vs Object keys forEach

Created: 5 years ago by: Guest

Jump to the latest result

For In

Object keys forEach

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):