Benchmark: for-in vs object.keys test TBM

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) { var x = key; } }
Object.keys
for (var i=10000; i > 0; i--) { Object.keys(obj).forEach(key => {var x = 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:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36

Browser/OS: Chrome 122 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
for-in	3715.9 Ops/sec
Object.keys	1412.7 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to help you understand what's being tested in this JavaScript benchmark.

**Benchmark Overview**

The benchmark measures the performance of two approaches for iterating over an object's properties: `for-in` and `Object.keys`. The test creates an object with 11 properties, each initialized to 1. The benchmark script then iterates over this object using both approaches, printing the value of a variable `x` assigned to each property key.

**Options Compared**

The two options being compared are:

1. **`for-in`**: This is a traditional loop construct in JavaScript that allows iteration over an object's properties using the property name as a variable.
2. **`Object.keys()`**: This method returns an array of property names for an object, which can be iterated over using a `forEach` loop.

**Pros and Cons**

* **`for-in`**:
	+ Pros: Can be more efficient in some cases, especially when iterating over objects with many properties.
	+ Cons: May not provide the expected results if the property names are non-string or have certain values (e.g., undefined, null).
* **`Object.keys()`**:
	+ Pros: Provides a consistent and predictable way to iterate over object properties, regardless of their type or value.
	+ Cons: May be less efficient than `for-in` for large objects due to the overhead of creating an array.

**Library**

None. The benchmark uses native JavaScript features only.

**Special JS Feature or Syntax**

No special syntax or features are used in this benchmark. However, it's worth noting that the `for-in` loop is sensitive to property names with certain values (e.g., undefined, null), which may affect its performance and accuracy.

**Other Alternatives**

If you're interested in optimizing JavaScript performance, here are some alternative approaches you might consider:

* **`Array.prototype.forEach()`**: This method provides a similar way to iterate over an array or object's properties as `Object.keys()`.
* **`for...of` loop**: Introduced in ECMAScript 2015, this loop construct allows iteration over iterable objects (e.g., arrays, sets) and provides a more concise syntax than traditional loops.
* **`Map` data structure**: A JavaScript implementation of the Map data structure can provide faster lookups and iteration over its keys.

Keep in mind that each approach has its trade-offs and may be suitable for different use cases. The choice ultimately depends on your specific requirements, performance constraints, and personal preference.

Related benchmarks:

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

Comparing performance of: for-in vs Object.keys

Created: 2 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

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