Benchmark: for-in hasOwnProperty vs 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) { if (obj.hasOwnProperty(key)) { console.log(key); } } }
Object.keys
for (var i=10000; i > 0; i--) { Object.keys(obj).forEach(key => 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 break down the benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark is designed to compare the performance of two approaches: `for-in` loop with `hasOwnProperty` check, and `Object.keys()` method with `forEach()` callback. The goal is to measure which approach is faster for iterating over an object's properties in a loop.

**Script Preparation Code**

The script preparation code defines an object `obj` with 11 properties, all initialized to the value 1. This object will be used as the test data for both benchmark approaches.

```javascript
var obj = {
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1
};
```

**Html Preparation Code**

The html preparation code is empty, which means that the benchmark doesn't generate any HTML code for testing. This is likely done to isolate the JavaScript performance comparison.

**Individual Test Cases**

There are two test cases:

1. **`for-in`**: This test case uses a traditional `for-in` loop with an `if` statement to check if each property exists using `hasOwnProperty`. The loop iterates over 10,000 iterations.
2. **`Object.keys()`**: This test case uses the `Object.keys()` method to get an array of the object's properties and then applies a `forEach()` callback function to log each property to the console. Again, the loop iterates over 10,000 iterations.

**Pros and Cons of Each Approach**

1. **`for-in`**: Pros:
	* Easy to read and understand for most developers.
	* Can be optimized using techniques like caching or memoization.
Cons:
	* Requires explicit checks for property existence (`hasOwnProperty`), which can lead to performance overhead.
	* Less predictable than other methods, as the loop order may vary.
2. **`Object.keys()`**: Pros:
	* More concise and expressive syntax.
	* Automatically handles null or undefined properties.
Cons:
	* May have performance overhead due to array iteration and callback function execution.

**Library: `Object.keys()`**

The `Object.keys()` method is a built-in JavaScript API that returns an array of the object's own enumerable property names. The purpose of this library-like API is to provide a convenient way to iterate over an object's properties without using traditional `for-in` loops.

**Special JS Feature/Syntax: None**

There are no special JavaScript features or syntax used in these benchmark approaches.

**Alternatives**

Other alternatives for iterating over an object's properties include:

1. **`for...in` with `.every()`**: This approach uses the `every()` method to check if all properties exist before logging them.
2. **`.forEach()` on a filtered array**: You could use the `filter()` method to exclude null or undefined properties and then iterate over the resulting array using `forEach()`.
3. **Native `Map` data structure**: If you're using modern JavaScript, you can create a `Map` object from your data and use its `keys()` method for iteration.

Keep in mind that these alternatives may have different performance characteristics or trade-offs compared to the original benchmark approaches.

Related benchmarks:

for-in hasOwnProperty vs 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):