Benchmark: for-in vs 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 (let i=10000; i > 0; i--) { for (let key in obj) { console.log(obj[key]); } }
Object.keys
for (let i=10000; i > 0; i--) { const keys = Object.keys(obj); for (let i = 0, iMax = keys.length, key; i < iMax; ++i) { console.log(obj[keys[i]]) } }

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 dive into the explanation of what is tested in this benchmark.

**Benchmark Definition**

The benchmark is comparing two approaches to iterate over an object's keys: `for-in` loop and `Object.keys()` method.

**Options being compared**

There are two options being compared:

1. **For-in loop**: This approach uses a traditional `for-in` loop to iterate over the object's properties.
2. **Object.keys() method**: This approach uses the `Object.keys()` method to get an array of the object's property names, and then iterates over that array using a traditional `for` loop.

**Pros and Cons**

* **For-in loop**:
	+ Pros: Can be more straightforward and easier to understand for some developers.
	+ Cons: May have performance issues if the object is large or if the iteration is needed multiple times, as it uses a proprietary method that may not be cached by browsers.
* **Object.keys() method**:
	+ Pros: Provides a standardized way of iterating over an object's properties, which can lead to better caching and performance.
	+ Cons: May require more code and setup for some developers.

**Library**

There is no specific library being used in this benchmark. However, the `Object.keys()` method is a built-in method in JavaScript that returns an array of the object's property names.

**Special JS feature or syntax**

There are two special aspects to note:

* **`for...in` loop**: This type of loop iterates over the properties of an object using its own property name as the loop variable. It is a proprietary method, not part of the standard JavaScript specification.
* **`const keys = Object.keys(obj);`**: This syntax uses destructuring assignment to extract the `keys` array from the result of calling `Object.keys()`. The `Object.keys()` method returns an array of strings representing the property names in the object.

**Other alternatives**

If you're interested in exploring alternative approaches, here are a few:

* **Using `forEach()`**: You can use the `forEach()` method on arrays to iterate over their elements. For example: `obj.keys().forEach(key => console.log(obj[key]));`
* **Using a traditional `for` loop with an index variable**: You can use a traditional `for` loop with an index variable, like this: `for (let i = 0; i < obj.length; i++) { const key = obj[i]; console.log(key); }`

Keep in mind that these alternatives may have slightly different performance characteristics compared to the two options being compared in this benchmark.

Related benchmarks:

for-in vs object.keys [2] (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):