Benchmark: for-in vs object.keys MT

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) { console.log(key); } }
Object.keys
for (var i=10000; i > 0; i--) { for (let 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
Object.keys

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 11 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36

Browser/OS: Chrome 136 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
for-in	8.0 Ops/sec
Object.keys	7.3 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 11 months ago):

LLMs can make mistakes. Check important info.

This benchmark compares two different ways of iterating over the properties of a JavaScript object: using the `for-in` loop and using `Object.keys()` with a `for-of` loop.

### Test Cases Breakdown

1. **Test Case - for-in**
   - **Code**: 
     ```javascript
     for (var i=10000; i > 0; i--) {
       for (var key in obj) {
           console.log(key);
       }
     }
     ```
   - **Method**: This uses the `for-in` loop to iterate over all enumerable properties of the `obj` object.
   - **Pros**:
     - Simple syntax that allows you to directly loop over object properties.
   - **Cons**:
     - Iterates over all enumerable properties, which may include properties inherited from the object's prototype chain. This can lead to unexpected results if not handled properly.
     - In some cases, performance may suffer due to checking properties along the prototype chain.

2. **Test Case - Object.keys**
   - **Code**: 
     ```javascript
     for (var i=10000; i > 0; i--) {
       for (let key of Object.keys(obj)) {
         console.log(key);
       }
     }
     ```
   - **Method**: This uses `Object.keys(obj)` to retrieve an array of the object's own enumerable property names and iterates over them using a `for-of` loop.
   - **Pros**:
     - Only iterates over the object's own properties, avoiding any inherited properties which could lead to cleaner results.
     - More predictable behavior and better encapsulation of the object's own attributes.
   - **Cons**:
     - May have additional overhead of creating an array of keys first, which could potentially lead to slower performance in some scenarios compared to a straightforward `for-in` loop, especially in cases with a large number of properties.

### Benchmark Results
- The benchmark results indicate the number of executions per second for each method. The `for-in` loop performed at approximately 7.99 executions per second, while the `Object.keys` method performed slightly lower at around 7.27 executions per second.

### Conclusion and Considerations
- **Performance**: The results suggest that, in this particular case and environment, the `for-in` loop is marginally faster than using `Object.keys`. However, the difference in performance should be weighed against the implications of control over property enumeration and potential for inherited enumerable properties, which might not be desired for all cases.
  
- **Usability**: When designing your code, you should consider whether you need to account for inherited properties or merely focus on the object’s own properties. If the latter is true, `Object.keys` is generally the safer and more predictable choice, despite a potential performance trade-off.
  
- **Alternatives**: Other alternatives to consider for iterating over object properties in modern JavaScript include:
  - **`Object.entries(obj)`**: This returns an array of key-value pairs, which can be more convenient for certain applications.
  - **`Object.values(obj)`**: If only values are needed, this allows you to access values without keys.
  - **`forEach` method on the array returned by `Object.keys()` or `Object.entries()`**: This provides a functional approach to iteration.

Ultimately, the choice between these methods will depend on specific project needs, performance requirements, and coding style preferences.

Related benchmarks:

for-in vs object.keys MT (version: 1)

Comparing performance of: for-in vs Object.keys

Created: 11 months 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 gpt-4o-mini, generated 11 months ago):