Benchmark: for-in vs for using object.keys 2

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) { if ({}.hasOwnProperty(obj, key)) { console.log(key); } } }
for
var keys = Object.keys(obj); for (var i=10000; i > 0; i--) { for (var j = 0; j < keys.length; j++ ) { console.log(keys[j]); } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for-in
for

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

This benchmark does not have any results yet. Be the first one to run it!

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

LLMs can make mistakes. Check important info.

I'll break down the benchmark and explain what's being tested, compared, and the pros and cons of each approach.

**Benchmark Overview**

The benchmark compares the performance of two ways to iterate over an object in JavaScript: `for-in` and using `Object.keys()`.

**What is being tested?**

1. **For-in**: This is a traditional way of iterating over an object's properties using the `in` keyword.
2. **Using Object.keys()**: This method returns an array of a given object's own enumerable property names, which can be used to iterate over the object.

**Options compared**

The benchmark compares the performance of:

1. **For-in**: The traditional way of iterating over an object's properties using `in`.
2. **Using Object.keys()**: Iterating over an object's properties by accessing its array of property names returned by `Object.keys()`.

**Pros and Cons of each approach:**

* **For-in**:
	+ Pros:
		- Often more readable and intuitive for simple iteration scenarios.
		- Can be useful when you need to access both the key and value in a single loop.
	+ Cons:
		- May not be as efficient, especially for large objects or arrays.
		- Can lead to unexpected behavior if used incorrectly (e.g., iterating over prototype chain properties).
* **Using Object.keys()**:
	+ Pros:
		- Generally more efficient and faster than `for-in`.
		- Avoids the potential issues with accessing prototype chain properties.
	+ Cons:
		- May be less readable or intuitive for complex iteration scenarios.
		- Requires an additional step to access the property names (e.g., using `keys.length` or `.forEach()`).

**Library usage**

In this benchmark, none of the libraries are explicitly mentioned. However, the use of `Object.keys()` implies that JavaScript's built-in object methods are being leveraged.

**Special JS feature/syntax**

This benchmark does not specifically test any special JavaScript features or syntax. It focuses on a fundamental aspect of iterating over objects in JavaScript: using `for-in` vs. using `Object.keys()`.

Related benchmarks:

for-in vs for using object.keys 2 (version: 0)

Comparing performance of: for-in vs for using object.keys

Comparing performance of: for-in vs for

Created: 5 years ago by: Guest

Jump to the latest result

for-in

for

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):