Benchmark: for-in hasOwnProperty vs object.keys for-of test vs for-in

Script Preparation code:

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

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for-in hasOwnProperty
Object.keys for-of
for-in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:104.0) Gecko/20100101 Firefox/104.0

Browser/OS: Firefox 104 on Windows

View result in a separate tab

Test name	Executions per second
for-in hasOwnProperty	2.4 Ops/sec
Object.keys for-of	2.3 Ops/sec
for-in	2.3 Ops/sec

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

LLMs can make mistakes. Check important info.

The provided JSON represents a benchmark test on MeasureThat.net, which compares the performance of three different approaches to iterate over an object's properties in JavaScript.

**Overview of the Benchmark**

The benchmark tests the execution speed of three methods:

1. `for-in` with `hasOwnProperty`
2. `Object.keys()` and `for-of` loops
3. Simple `for-in` loop

The test creates a large object (`obj`) with 11 properties and iterates over it using each of these approaches, logging the keys to the console.

**Comparison of Approaches**

1. **For-in with hasOwnProperty**: This approach uses the `in` operator to iterate over the object's own enumerable properties, and then checks if each property is a direct property of the object using `hasOwnProperty`. This method can be slow because it needs to check each property individually.
2. **Object.keys() and for-of loops**: `Object.keys()` returns an array of the object's own enumerable property names. The `for-of` loop iterates over this array, logging each key to the console. This approach is likely faster than the first one because it avoids the need for individual checks with `hasOwnProperty`.
3. **Simple for-in loop**: This approach uses a traditional `for-in` loop without any additional checks. It's likely faster than the first two approaches but may not be as efficient as the second one.

**Pros and Cons of Each Approach**

1. **For-in with hasOwnProperty**:
	* Pros: Simple to implement, no need for additional libraries or modules.
	* Cons: Slow due to individual property checks.
2. **Object.keys() and for-of loops**:
	* Pros: Faster than the first approach, avoids individual property checks.
	* Cons: Requires knowledge of `Object.keys()` and `for-of` syntax.
3. **Simple for-in loop**:
	* Pros: Simple to implement, likely faster than the first approach.
	* Cons: May not be as efficient as the second approach.

**Library Used**

The benchmark uses `Object.keys()` and the `for-of` loop, which are built-in JavaScript features. No additional libraries or modules are required.

**Special JS Feature/Syntax**

None mentioned in the provided code. However, it's worth noting that `Object.keys()` was introduced in ECMAScript 5 (ES5), and `for-of` loops were introduced in ECMAScript 2015 (ES6).

**Alternative Approaches**

Other approaches to iterate over an object's properties might include:

1. Using `Array.prototype.forEach()` or other array methods.
2. Implementing a custom iterator using `Symbol.iterator` or `Array.prototype[Symbol.iterator]`.
3. Using a library like Lodash or Ramda, which provide utility functions for working with objects and arrays.

Keep in mind that the performance differences between these approaches may be negligible in most cases, and the choice of approach should be guided by factors such as code readability, maintainability, and personal preference.

Related benchmarks:

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

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

Created: 2 years ago by: Guest

Jump to the latest result

for-in hasOwnProperty

Object.keys for-of

for-in

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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