Benchmark: for..in vs object.keys grtynhdtfym

Script Preparation code:

let obj = {
        a: 1,
        b: [],
        c: 'abc',
        d: Symbol('test')
    },
    keys = Object.keys(obj).keys()

Tests:

for...in
for (let prop in obj) console.log(prop)
Object.keys.keys
for (let prop of keys) console.log(prop)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for...in
Object.keys.keys

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 21 days ago)

User agent: Mozilla/5.0 (X11; CrOS x86_64 14541.0.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36

Browser/OS: Chrome 126 on Chrome OS 14541.0.0

View result in a separate tab

Test name	Executions per second
for...in	11038.6 Ops/sec
Object.keys.keys	29526024.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 21 days ago):

LLMs can make mistakes. Check important info.

The benchmark defined in the JSON provided compares two different approaches to iterating over the properties of an object in JavaScript: using the `for..in` loop and using `Object.keys()`. Here’s a detailed breakdown of the benchmark, the approaches being tested, their pros and cons, and other considerations:

### Approaches Compared

1. **`for..in` Loop**:
    - **Benchmark Definition**: `for (let prop in obj) console.log(prop)`
    - **Description**: The `for..in` loop iterates over the enumerable properties of an object. It will return property names (keys) as strings.
    - **Pros**:
        - Simple and straightforward syntax for looping over an object’s properties.
        - Can be used to iterate over the properties of any object, including those inherited from the prototype chain.
    - **Cons**:
        - Includes properties that are inherited from the prototype chain, which may not be desirable in many cases. This can lead to unexpected behavior if the prototype is extended or modified.
        - Performance can be questionably slower, especially for larger objects or those with many enumerable properties, since every property needs to be checked.
        
2. **`Object.keys()` Method**:
    - **Benchmark Definition**: `for (let prop of keys) console.log(prop)`
    - **Description**: This approach uses the `Object.keys()` method to get an array of a given object’s own enumerable property names (keys), which is then iterated over with a `for...of` loop.
    - **Pros**:
        - Only returns the object's own properties, avoiding those that may be inherited from the prototype chain. This is often a desired behavior.
        - Generally faster than `for..in` for iterating over a smaller set of properties.
    - **Cons**:
        - Slightly more overhead due to the creation of an array containing the keys before iteration.
        - Not supported in older JavaScript environments, but it is well-supported in modern browsers.

### Performance Comparison

Based on the latest benchmark results provided:

- **`Object.keys.keys`**: Achieved **29,526,024 executions per second**.
- **`for...in`**: Achieved **11,038.59 executions per second**.

This stark difference in performance indicates that using `Object.keys()` is significantly more efficient for the given test conditions, confirming the expectations around the speed of these two iteration methods.

### Other Considerations

- **Use Case Scenarios**: When deciding which method to use, consider the nature of the object you are working with. If you require only the object's own properties (like when dealing with plain objects), `Object.keys()` is the clearer choice. If you want to include inherited properties or are dealing with prototypes, `for..in` may be appropriate, but it requires additional checks to avoid unintended behavior.
  
- **Alternative Methods**:
    - **`Object.entries()`**: Similar to `Object.keys()`, but returns an array of key-value pairs, which can be useful if both keys and values are needed during iteration.
    - **`forEach()` on `Object.keys()`**: This provides a functional programming style but may not have the same performance benefits in very large data sets compared to the traditional `for..of` method.
    - **`Map` objects**: If order of properties matters or if you want a collection without prototype chain interactions, you might consider using `Map`, which maintains the order of insertion and only contains its own properties.

In conclusion, for the specific benchmark comparing `for..in` and `Object.keys()`, the latter proves to be the clearer and more performant option for most cases where one is only interested in the object's own properties. Choosing the right iteration method depends greatly on the specific requirements of the task at hand.

Related benchmarks:

for..in vs object.keys grtynhdtfym (version: 1)

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

Created: 21 days ago by: Guest

Jump to the latest result

for...in

Object.keys.keys

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated 21 days ago):