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

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.

Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Overview**

The provided benchmark compares two approaches to iterate over an object's keys: `for-in` and using the `Object.keys()` method with a `for...of` loop. The goal is to determine which approach is faster, if any.

**Options Compared**

Two options are being compared:

1. **For-in**: This approach uses a traditional `for` loop with an incrementing variable (`i`) to iterate over the object's keys. The loop iterates over the object's own enumerable properties using the `in` operator.
2. **Object.keys() with for...of**: This approach uses the `Object.keys()` method to get an array of the object's keys, and then uses a `for...of` loop to iterate over that array.

**Pros and Cons**

### For-in

Pros:

* Wide browser support (including older browsers)
* Can be used in situations where you need to access both the key and value of each property
* Does not require an additional library or module

Cons:

* Less efficient than other methods, especially for large objects
* Can be slower due to the overhead of the `in` operator
* May not be suitable for use with complex objects or objects that have many inherited properties

### Object.keys() with for...of

Pros:

* More efficient than traditional `for-in`, especially for large objects
* Provides a more modern and concise way of iterating over object keys
* Does not require an additional variable to keep track of the current key

Cons:

* Less browser support (some older browsers may not support it)
* May not work as expected if the object has inherited properties or other complex scenarios
* Requires JavaScript version 2015 (ECMAScript 6) or later

**Library/Module**

The `Object.keys()` method is a built-in method of the `Object` prototype in modern JavaScript. It returns an array of a given object's own enumerable property names.

**Special JS Feature/Syntax**

In this benchmark, no special JavaScript features or syntax are being used beyond what's described above. However, if you were to write your own benchmark for other scenarios, you might use features like:

* `Set` objects for faster iteration over unique values
* `Map` objects for faster iteration over key-value pairs
* `Array.prototype.reduce()` and similar methods for reducing an array to a single value

**Other Alternatives**

If you want to compare different approaches to iterating over object keys, you could also consider the following alternatives:

1. **Using a traditional `for` loop with an array index**: This approach is similar to using `Object.keys()`, but instead of using an array, you use a numeric variable to iterate over the object's keys.
2. **Using `Array.prototype.forEach()` and `Map.prototype.forEach()`**: These methods provide a more concise way to iterate over arrays and objects, respectively.
3. **Using `Set.prototype.forEach()`**: This method provides a fast and efficient way to iterate over unique values.

Keep in mind that each of these alternatives has its own trade-offs in terms of efficiency, browser support, and readability.

Related benchmarks:

for-in vs for key of Object.keys (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):