Benchmark: Object length (for-in vs object.keys)

Script Preparation code:

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

Tests:

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

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:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 120 on Android

View result in a separate tab

Test name	Executions per second
for-in	6.6 Ops/sec
Object.keys	6.6 Ops/sec

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

LLMs can make mistakes. Check important info.

**Benchmark Explanation**

The provided JSON represents a JavaScript microbenchmark on MeasureThat.net, which compares the performance of two approaches for iterating over an object's properties: the traditional `for-in` loop and the `Object.keys()` method.

**Options Compared**

Two options are compared:

1. **Traditional `for-in` loop**: This approach uses a traditional `for` loop with a manual index variable (`i`) to iterate over the object's properties.
2. **`Object.keys()` method**: This approach uses the `Object.keys()` method, which returns an array of property names in the specified object.

**Pros and Cons**

* **Traditional `for-in` loop**:
	+ Pros: Can be more flexible and allow for manual iteration over specific properties or arrays.
	+ Cons: May have performance issues due to the need for a manual index variable and potential type coercion.
* **`Object.keys()` method**:
	+ Pros: Is generally faster and more concise, as it uses an optimized array of property names.
	+ Cons: May not be as flexible as the traditional `for-in` loop, as it only returns an array of property names.

**Other Considerations**

Both approaches have performance implications:

* The `Object.keys()` method is typically faster because it avoids the need for a manual index variable and type coercion.
* However, the traditional `for-in` loop can be optimized by using `Object.getOwnPropertyNames()` or `Object.keys()` with an array-like object (e.g., `{...}`), which reduces overhead.

**Library Used**

The benchmark uses the JavaScript `Object` and `Array` prototypes to create a sample object (`obj`) and retrieve its property names using `Object.keys()`. The `for-in` loop is implemented manually, without any external libraries or helpers.

**Special JS Feature/Syntax**

There are no special JavaScript features or syntax used in this benchmark. Both approaches only use standard JavaScript constructs (variables, data types, loops).

**Other Alternatives**

If you were to create a similar benchmark for other object iteration methods, some alternatives might include:

* `Array.prototype.forEach()`: A more concise and modern way to iterate over arrays.
* `for...of` loop: An older, yet still supported, way to iterate over arrays and objects using destructuring syntax.
* `map()` and `reduce()` methods: Can be used to perform more complex operations on array-like objects.

These alternatives might not directly compare with the traditional `for-in` loop or `Object.keys()` method but could provide additional insights into JavaScript's iteration capabilities.

Related benchmarks:

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

Comparing performance of: for-in vs Object.keys

Created: 2 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

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