Benchmark: for-in vs object.keys in loop

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 (var 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

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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 on MeasureThat.net.

The provided JSON represents a benchmark test case that compares two approaches to iterate over an object: `for-in` loop and using `Object.keys()` method.

**Tested Options**

1. **For-in Loop**: This approach uses a traditional `for` loop with the `in` keyword to iterate over the object's properties.
2. **Using 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 `for...of` loop.

**Pros and Cons**

* **For-in Loop**:
	+ Pros: Simple, straightforward, and widely supported.
	+ Cons: Can be slower due to the overhead of the `in` operator and potential issues with property names (e.g., case sensitivity).
* **Using Object.keys() Method**:
	+ Pros: More concise and efficient than the `for-in` loop, especially for modern browsers that support `Object.keys()`.
	+ Cons: Requires more code, and if not done correctly, can lead to performance issues or errors.

**Library Usage**

In this benchmark, the `Object.keys()` method is used from the built-in JavaScript `Object` prototype. This is a standard library function that returns an array of a given object's property names.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax used in this benchmark. The code only relies on basic JavaScript constructs and libraries (in this case, the built-in `Object` prototype).

**Other Alternatives**

If you're looking for alternative ways to iterate over an object, consider:

1. **Using a traditional for loop**: Similar to the `for-in` loop, but without the `in` keyword.
2. **Using a while loop**: Iterates over the properties using a numeric index.
3. **Using the Array.prototype.forEach() method**: Iterates over the array of property names returned by `Object.keys()` or other methods.

Here's an example of how you could rewrite the benchmark test case using these alternatives:

```javascript
// Using a traditional for loop
var i = 0;
while (i < 10000) {
  for (var key in obj) {
    console.log(key);
  }
}

// Using a while loop
var i = 9999;
while (i >= 0) {
  var key;
  for (key in obj) {
    console.log(key);
  }
}

// Using the Array.prototype.forEach() method
Object.keys(obj).forEach(function(key) {
  console.log(key);
});
```

Keep in mind that these alternatives may have different performance characteristics, and MeasureThat.net might not include them in their benchmark results.

Related benchmarks:

for-in vs object.keys in loop (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):