Benchmark: for-in vs object.keys map array

Script Preparation code:

var obj = {
    '1': 1,
    '2': 1,
    '3': 1,
    '4': 1,
    '5': 1,
    '6': 1,
    '7': 1,
    '8': 1,
    '9': 1,
    '10': 1
};

Tests:

for-in
for (var i=10000; i > 0; i--) { const arr = []; for (var key in obj) { arr.push(key); } }
Object.keys
for (var i=10000; i > 0; i--) { Object.keys(obj).map(key => key); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for-in
Object.keys

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's break down what's being tested in the provided JSON benchmark.

**Benchmark Definition**

The benchmark is comparing three approaches to iterate over an array of keys from an object:

1. **For-in loop**: This approach uses a traditional `for` loop with `var i = 10000; i > 0; i--` and iterates over the object's properties using `for (var key in obj)`.
2. **Object.keys() method**: This approach uses the built-in `Object.keys()` method to get an array of keys from the object, and then maps over it using `map(key => key)`.
3. **Array map() method**: Although not explicitly mentioned, this is implied by the context. The third test case seems to be a mistake and should compare the performance of the Object.keys() vs an array's map() function.

**Options compared**

The benchmark is comparing two specific approaches:

* For-in loop
* Object.keys()

Additionally, it implies a comparison with an array's `map()` method, although this is not explicitly stated in the provided test cases.

**Pros and Cons of each approach:**

1. **For-in loop**:
	* Pros:
		+ Easy to read and understand for developers familiar with JavaScript.
		+ Can be optimized by using a `for` loop with an index variable, which can be faster than iterating over the object's properties.
	* Cons:
		+ Not as efficient as other methods, especially when dealing with large objects or arrays, since it iterates over the object's properties and assigns each property value to a variable.
2. **Object.keys() method**:
	* Pros:
		+ More efficient than the for-in loop approach, especially for large datasets, since it returns an array of keys in a single operation.
	* Cons:
		+ Can be slower if the resulting array needs to be processed further (e.g., using `map()` or `forEach()`).
3. **Array map() method**:
	* Pros:
		+ Efficient for large datasets, as it uses a more optimized algorithm internally.
	* Cons:
		+ Implies a conversion step from an object's keys to an array, which can be slower than the Object.keys() method.

**Library and purpose**

The `Object.keys()` method is a built-in JavaScript function that returns an array of strings representing the property names of a given object. It is part of the ECMAScript standard and provides a convenient way to iterate over an object's properties.

**Special JS feature or syntax**

There are no special features or syntax used in this benchmark, other than the use of the `map()` method on arrays.

**Other alternatives**

In addition to the three approaches mentioned, some developers might also consider using:

* **For...of loop**: A more modern and efficient way to iterate over an object's properties. However, it is not included in this benchmark.
* **Array.from() method**: Another way to create an array from an iterable, which can be used instead of Object.keys().

Related benchmarks:

for-in vs object.keys map array (version: 0)

Comparing performance of: for-in vs Object.keys

Created: 3 years ago by: Guest

Jump to the latest result

for-in

Object.keys

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):