Benchmark: for-in vs object.keys (no hof in 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) { console.log(key); } }
Object.keys
for (var i=10000; i > 0; i--) { for (var 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: one year ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36

Browser/OS: Chrome 130 on Linux

View result in a separate tab

Test name	Executions per second
for-in	2.0 Ops/sec
Object.keys	1.9 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one year ago):

LLMs can make mistakes. Check important info.

The benchmark described on MeasureThat.net evaluates the performance differences between two approaches for iterating over the properties of an object in JavaScript: the `for-in` loop and the `Object.keys` method with a `for-of` loop.

### Benchmark Overview

1. **Test Cases:**
   - **`for-in` Loop:**
     ```javascript
     for (var i = 10000; i > 0; i--) {
         for (var key in obj) {
             console.log(key);
         }
     }
     ```
   - **`Object.keys` with `for-of`:**
     ```javascript
     for (var i = 10000; i > 0; i--) {
         for (var key of Object.keys(obj)) console.log(key);
     }
     ```

### Comparison of Approaches

- **`for-in` Loop:**
  - **Pros:**
    - Simpler syntax for directly iterating over object properties.
    - Enumerates all properties, including those in the prototype chain if not filtered.
  - **Cons:**
    - Can potentially iterate over inherited properties, leading to unexpected behavior if the object is extended or modified.
    - Performance may vary based on the number of properties and the complexity of the prototype chain.

- **`Object.keys` with `for-of`:**
  - **Pros:**
    - Only returns the object's own properties (not inherited), making it safer to use when you want to avoid prototype interference.
    - Generally performs better in modern JavaScript engines, particularly for medium to large-sized objects.
  - **Cons:**
    - Requires an additional method call (`Object.keys`), adding potential overhead, although most engines optimize this.

### Results Interpretation

From the provided benchmark results:
- The `for-in` loop executed approximately **2.04 executions per second**.
- The `Object.keys` method executed approximately **1.89 executions per second**.

These results suggest that, in this particular environment and scenario, the `for-in` loop performed better than `Object.keys`. However, performance can vary significantly based on context and browser optimizations.

### Other Considerations

1. **Performance Variations:**
   - The performance observed may depend on numerous factors, including the JavaScript engine in use, the current execution context, and even the specific hardware or system state.
   - It's essential to conduct benchmarks in the targeted environments where your code will run to obtain meaningful results.

2. **Alternatives:**
   - **`forEach` Loop:** This approach, with an array of the keys via `Object.keys(obj).forEach(...)`, provides a more functional programming style. However, it may be slower due to the overhead of function calls.
   - **`for...in` along with `hasOwnProperty`:** To avoid inherited properties, one can pair `for-in` with `hasOwnProperty` checks.
   - **ES6 Features:** The `Object.entries()` and `Object.values()` methods can be alternatives for accessing both keys and values or just values, respectively, using similar loops.

### Conclusion

In summary, the benchmark compares two common methods for iterating over property keys in JavaScript. While both approaches have their advantages and disadvantages, the choice of which to use often depends on the specific requirements of the task, including considerations for safety and performance. Software engineers should choose based on the context of their usage, conducting performance tests in their actual execution environments for the best insights.

Related benchmarks:

for-in vs object.keys (no hof in Object.keys) (version: 1)

Comparing performance of: for-in vs Object.keys

Created: one year 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 one year ago):