Benchmark: for-in vs object.keys for-of

Script Preparation code:

var obj = {
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1
};

Tests:

for-in
for (var i=10000; i > 0; i--) { for (var key in obj) { console.log(key); } }
Object.keys
for (var i=10000; i > 0; i--) { for (var key of Object.keys(obj)) { console.log(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:

No previous 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 the provided benchmark and explain what's being tested.

**Benchmark Purpose:**

MeasureThat.net is testing two approaches for iterating over an object in JavaScript:

1. **For-in loop**: This loop iterates over an object using its property names (i.e., keys).
2. **Object.keys() function**: This method returns an array of a given object's own enumerable property names.

**Options being compared:**

The benchmark is comparing the performance of these two approaches:

* For-in loop
* Object.keys() function

**Pros and Cons:**

1. **For-in loop**:
	* Pros:
		+ Can iterate over objects with non-enumerable properties (i.e., properties that are not included in the object's prototype chain).
		+ Does not require the object to be in a specific state (e.g., not being modified by other scripts).
	* Cons:
		+ May iterate over non-enumerable properties, which can lead to unexpected behavior.
		+ Can be slower due to the overhead of property lookup and iteration.
2. **Object.keys() function**:
	* Pros:
		+ Is a built-in method that is optimized for performance.
		+ Does not require iterating over non-enumerable properties.
	* Cons:
		+ Only iterates over enumerable properties, which may exclude some properties from the object.

**Library usage:**

None of the benchmark tests use any external libraries. The `Object.keys()` function is a built-in method in JavaScript.

**Special JS features or syntax:**

There are no special JavaScript features or syntax being tested in this benchmark.

**Other considerations:**

Keep in mind that this benchmark only compares two specific approaches for iterating over an object. Other factors, such as the object's size, complexity, and contents, may affect performance.

**Alternative approaches:**

Other approaches for iterating over an object in JavaScript include:

* **For...of loop**: This is a newer iteration method introduced in ECMAScript 2015 (ES6). It can be used to iterate over objects using the `for...of` statement.
* **Array.prototype.forEach()**: This method iterates over arrays and objects that support iterative protocols. However, it may not work as expected for all types of objects.

In summary, this benchmark is testing the performance of two approaches for iterating over an object in JavaScript: the traditional For-in loop and the Object.keys() function. The results can help developers understand which approach to use depending on their specific use case.

Related benchmarks:

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

Comparing performance of: for-in vs Object.keys

Created: 5 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):