Benchmark: for-in vs for-in hasOwnProperty vs object.keys forEach

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(key); } }
for-in hasOwnProperty
for (let i=10000; i > 0; i--) { for (let key in obj) { if (Object.prototype.hasOwnProperty.call(obj, key)) { console.log(key); } } }
Object.keys forEach
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
for-in hasOwnProperty
Object.keys forEach

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

**Benchmark Explanation**

The provided JSON represents a JavaScript microbenchmarking test on the MeasureThat.net website. The benchmark compares three approaches for iterating over an object: `for-in`, `for-in` with `Object.prototype.hasOwnProperty.call()`, and `Object.keys()` followed by `forEach`.

**What is being tested?**

Each individual test case measures the performance of a specific iteration approach:

1. **`for-in`**: Iterates over the object's own enumerable properties using the `in` operator.
2. **`for-in` with `hasOwnProperty`**: Iterates over the object's own enumerable properties, filtering out inherited properties by checking if each property is present on the prototype chain using `Object.prototype.hasOwnProperty.call()`.
3. **`Object.keys()` followed by `forEach`**: Uses the `Object.keys()` method to get an array of the object's own enumerable property names, and then iterates over this array using the `forEach` method.

**Options compared**

The benchmark compares these three approaches to determine which one performs best in terms of execution speed. The options are:

1. **`for-in`**: Simple iteration using the `in` operator.
2. **`for-in` with `hasOwnProperty`**: Filtering out inherited properties.
3. **`Object.keys()` followed by `forEach`**: Using an array-based approach.

**Pros and Cons**

Here's a brief analysis of each approach:

1. **`for-in`**:
	* Pros: Simple, easy to understand, and efficient for small objects.
	* Cons: May iterate over inherited properties, which can lead to slower performance for large objects or complex inheritance hierarchies.
2. **`for-in` with `hasOwnProperty`**:
	* Pros: Filters out inherited properties, potentially improving performance for large objects or complex inheritance hierarchies.
	* Cons: Adds a small overhead due to the extra check, which can negate some of the benefits for very small objects or simple iteration scenarios.
3. **`Object.keys()` followed by `forEach`**:
	* Pros: Efficient and concise way to iterate over an object's own enumerable properties without having to worry about inherited properties.
	* Cons: Requires access to modern JavaScript features (ECMAScript 2015+), which may not be supported in older browsers or environments.

**Library and Special JS Features**

The benchmark uses the following library:

1. **`Object.keys()`**: A built-in method introduced in ECMAScript 2015, which returns an array of the object's own enumerable property names.
2. **`forEach`**: Also a built-in method introduced in ECMAScript 2015, which allows iterating over arrays and other iterable objects.

**Other Considerations**

When choosing between these approaches, consider the following:

1. **Object size and complexity**: For small to medium-sized objects with simple inheritance hierarchies, `for-in` may be sufficient. For large or complex objects, filtering out inherited properties using `hasOwnProperty` might improve performance.
2. **Browser support**: If you need to support older browsers that don't support modern JavaScript features, you may need to use alternative approaches like `for-in` with a loop or manually iterating over the object's properties.

**Alternatives**

If you're looking for alternatives to these approaches, consider:

1. **Using a library or framework**: Some libraries, such as Lodash, provide optimized iteration functions that can outperform the built-in methods.
2. **Caching or memoization**: If you need to iterate over an object multiple times with similar properties, consider caching the result or using memoization techniques to improve performance.

Keep in mind that the best approach depends on your specific use case and requirements.

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.114 Safari/537.36

Browser/OS: Chrome 91 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
for-in	1.2 Ops/sec
for-in hasOwnProperty	1.1 Ops/sec
Object.keys forEach	0.8 Ops/sec

Related benchmarks:

for-in vs for-in hasOwnProperty vs object.keys forEach (version: 0)

for-in for-in hasOwnProperty object.keys forEach

Comparing performance of: for-in vs for-in hasOwnProperty vs Object.keys forEach

Created: 3 years ago by: Guest

Jump to the latest result

for-in

for-in hasOwnProperty

Object.keys forEach

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):