Benchmark: for-in with hasOwnProperty guard 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 ({}.hasOwnProperty.call(obj, 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):

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Let's break down the benchmark and explain what's being tested.

**Benchmark Definition**
The benchmark is designed to compare two approaches for iterating over an object in JavaScript:

1. `for-in` loop with a guard clause using `hasOwnProperty()`.
2. Using the `Object.keys()` method and the `forEach()` method.

**Options Compared**

* **For-in loop**: This approach uses the `for-in` loop, which iterates over the property names of an object. The `for-in` loop has access to both the property name and value through the `in` keyword.
* **Using Object.keys() and forEach()**: This approach uses the `Object.keys()` method to get an array of the object's property names, and then uses the `forEach()` method to iterate over that array.

**Pros and Cons**

* **For-in loop with hasOwnProperty() guard**:
	+ Pros: can handle objects with inherited properties, allows for early exit if a property is not present.
	+ Cons: can be slower due to the overhead of checking `hasOwnProperty()`, may not work correctly in older browsers that don't support it.
* **Using Object.keys() and forEach()**:
	+ Pros: faster and more modern approach, works consistently across all browsers, doesn't require explicit checks for property presence.
	+ Cons: requires an extra step to get the array of property names, may not work correctly if the object has inherited properties.

In general, the `Object.keys()` and `forEach()` approach is faster and more concise, but it may not be suitable for all use cases. The `for-in` loop with a `hasOwnProperty()` guard provides more control over iteration, but may have performance implications.

**Library/Module Used**
None explicitly mentioned in the benchmark definition. However, the `Object.keys()` method is a built-in JavaScript method that returns an array of a given object's property names. The `forEach()` method is also a built-in JavaScript method that iterates over an array and executes a callback function for each element.

**Special JS Features/ Syntax**
None explicitly mentioned in the benchmark definition. However, it's worth noting that the `for...in` loop has some nuances, such as:

* Inherited properties: when iterating over an object's own property names, the `for-in` loop also includes inherited properties.
* Property order: the order of property iteration is not guaranteed and may vary across browsers.

In this benchmark, we can assume that the authors are focusing on the performance difference between these two approaches rather than exploring edge cases or using specialized features.

Related benchmarks:

for-in with hasOwnProperty guard 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):