Benchmark: for-in vs object.keys (own props)

Script Preparation code:

var obj = {
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1
};
var o1, lo1, io1, vo1, ko1, ko1s;

Tests:

for-in
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 (var i=10000; i > 0; i--) { o1 = obj; ko1s = Object.keys(o1); lo1 = ko1s.length; for(io1=0; io1<lo1; io1++) { ko1 = ko1s[io1]; vo1 = o1[ko1]; console.log(ko1) } }

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 provided benchmark and explain what is being tested.

**Benchmark Overview**

The benchmark is designed to compare the performance of two approaches for iterating over an object's properties: `for-in` loop and `Object.keys()` method with a loop.

**Script Preparation Code**

The script preparation code sets up an object `obj` with 7 properties, all initialized with the value 1. This object will be used as input for both benchmarking scenarios.

**Benchmark Test Cases**

There are two individual test cases:

1. **"for-in"`**: This test case uses a traditional `for-in` loop to iterate over the object's properties. The loop iterates from 10,000 down to 0, and for each iteration, it prints out the current property value using `console.log(key)`.
2. **"Object.keys"`**: This test case uses the `Object.keys()` method to get an array of the object's property names, and then loops over this array using a traditional `for` loop. For each iteration, it accesses the corresponding property on the original object using the bracket notation (`o1[ko1]`) and prints out its value using `console.log(ko1)`.

**Library Used**

In both test cases, no external libraries are used beyond the built-in JavaScript `Object` and `Array` objects. However, it's worth noting that some browsers may have additional libraries or features that might affect the benchmark results.

**Special JS Features/Syntax**

This benchmark does not explicitly use any special JavaScript features or syntax. It relies on standard JavaScript constructs like loops, objects, and arrays.

**Comparison of Approaches**

The two approaches differ in how they iterate over the object's properties:

* `for-in` loop: Iterates directly over the object's property names using a proprietary syntax (`var key in obj`). This approach allows for direct access to the property name, but can be slower due to its proprietary nature.
* `Object.keys()` method with a loop: Uses the `Object.keys()` method to get an array of property names and then loops over this array. This approach is generally faster and more efficient than the `for-in` loop, as it leverages the optimized implementation of `Object.keys()`.

**Pros and Cons**

* **For-in**: Pros:
	+ Direct access to property name
	+ Can be useful in certain scenarios where property names are important
*	Cons:
	+ Proprietary syntax
	+ May be slower due to its proprietary nature
* **Object.keys() method with a loop**:
	+ Generally faster and more efficient than `for-in`
	+ Leverages optimized implementation of `Object.keys()`

**Other Alternatives**

If you're looking for alternative approaches, you could consider using other methods like:

* Using the `forEach()` method on an array of property names
* Using a library like Lodash or Ramda to iterate over objects

However, these alternatives may not be as efficient or straightforward as the original `Object.keys()` approach.

I hope this explanation helps!

Related benchmarks:

for-in vs object.keys (own props) (version: 0)

Comparing performance of: for-in vs Object.keys

Created: 4 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):