Benchmark: for-in with hasOwnProperty vs for-of over Object.keys

Script Preparation code:

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

Tests:

for-in with hasOwnProperty
var hasOwn = Object.prototype.hasOwnProperty; for (var key in obj) { if (hasOwn.call(obj, key)) { console.log(key); } }
Object.keys
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 with hasOwnProperty
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 Purpose**

The benchmark compares two approaches for iterating over an object in JavaScript:

1. `for-in` with `hasOwnProperty`
2. `Object.keys`

Both methods aim to iterate over the properties of an object, but they differ in how they access and process these properties.

**for-in with hasOwnProperty**

This approach uses a traditional `for-in` loop to iterate over the object's properties. However, it relies on the `hasOwnProperty` method to check if each property is owned by the object itself (i.e., not inherited from its prototype). This ensures that only own properties are processed.

Pros:

* Easy to understand and implement
* Works well with objects that have a large number of own properties

Cons:

* Can be slower due to the overhead of checking ownership using `hasOwnProperty`
* May not perform as well on objects with a large number of inherited properties

**Object.keys**

This approach uses the `Object.keys()` method to get an array of an object's own enumerable property names. The loop then iterates over this array, logging each property.

Pros:

* Faster execution compared to `for-in` with `hasOwnProperty`
* More concise and efficient

Cons:

* May not work well on objects that have a large number of inherited properties (since `Object.keys()` only returns own enumerable properties)
* Requires support for the `Object.keys()` method, which was introduced in ECMAScript 5 (ES5)

**Other Considerations**

Both approaches have some additional considerations:

* For objects with many inherited properties, the `for-in` loop may still be slower due to the overhead of checking ownership.
* Using `Object.keys()` can lead to performance issues if the object is very large or has a large number of own enumerable properties.

**Library and Special JS Features**

There are no specific libraries used in this benchmark. However, it does rely on the JavaScript language itself, specifically:

* The `for-in` loop
* The `hasOwnProperty()` method (part of the `Object` prototype)
* The `Object.keys()` method (introduced in ECMAScript 5)

**Other Alternatives**

If you're interested in exploring alternative approaches, some options include:

* Using a library like Lodash or Ramda for functional programming and iterating over objects
* Utilizing modern JavaScript features like `for...of` loops with iterable objects (e.g., arrays, sets)
* Leveraging WebAssembly or other low-level language features for performance-critical code

Related benchmarks:

for-in with hasOwnProperty vs for-of over Object.keys (version: 0)

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

Created: 4 years ago by: Guest

Jump to the latest result

for-in with hasOwnProperty

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):