Benchmark: for-in vs for-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:

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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 world of JavaScript microbenchmarks!

**Benchmark Overview**

The provided JSON represents a benchmark test case on MeasureThat.net, which compares the performance of two approaches: using a traditional `for-in` loop versus using the `Object.keys()` method to iterate over an object. The goal is to determine which approach is faster.

**Script Preparation Code**

The script preparation code defines an object `obj` with six properties, each containing the value `1`. This object will be used as input for both benchmark tests.
```javascript
var obj = {
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1
};
```
**Html Preparation Code**

There is no HTML preparation code, which means that the benchmark tests are standalone JavaScript snippets.

**Individual Test Cases**

There are two test cases:

1. **`for-in`**: This test case uses a traditional `for-in` loop to iterate over the object's properties.
```javascript
for (var i=10000; i > 0; i--) {
  for (var key in obj) {
    console.log(key);
  }
}
```
This approach uses the `in` operator to access the object's properties and logs each property name to the console.

2. **`Object.keys()`**: This test case uses the `Object.keys()` method to iterate over the object's properties.
```javascript
for (var i=10000; i > 0; i--) {
  for(const key of Object.keys(obj)){
    console.log(key);
  }
}
```
This approach uses the `Object.keys()` method to get an array of property names and then loops through it using a `for...of` loop.

**Pros and Cons**

Here are some pros and cons of each approach:

* **Traditional `for-in` loop**:
	+ Pros: Simple, straightforward implementation.
	+ Cons: Can be slow due to the use of `in` operator, which may perform additional checks.
* **`Object.keys()` method**:
	+ Pros: Faster, as it avoids the use of `in` operator and provides a more efficient way to iterate over object properties.
	+ Cons: Requires the use of `Object.keys()`, which can add overhead.

**Library**

In this benchmark, the `Object.keys()` method is used, which is a built-in JavaScript method that returns an array-like object containing the property names of an object. The purpose of using `Object.keys()` is to provide a more efficient way to iterate over the object's properties without relying on the `in` operator.

**Special JS Feature**

There are no special JavaScript features or syntax used in this benchmark, such as async/await, generators, or decorators.

**Other Alternatives**

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

* **Using `for...of` loop with `Object.entries()`**: Instead of using `Object.keys()`, you could use the `Object.entries()` method to get an array of key-value pairs and then iterate over it using a `for...of` loop.
```javascript
for (var i=10000; i > 0; i--) {
  for(const [key, value] of Object.entries(obj)){
    console.log(key);
  }
}
```
This approach would provide similar performance to the `Object.keys()` method.

* **Using `Array.prototype.forEach()`**: You could also use the `Array.prototype.forEach()` method to iterate over an array of property names returned by `Object.keys()`.
```javascript
for (var i=10000; i > 0; i--) {
  Object.keys(obj).forEach(key => console.log(key));
}
```
This approach would provide similar performance to the `Object.keys()` method.

I hope this explanation helps you understand the benchmark and its approaches!

Related benchmarks:

for-in vs for-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):