Benchmark: for-in vs object.keys for checking empty

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) { if (key) return; } }
Object.keys
for (var i=10000; i > 0; i--) { if (!Object.keys(obj).length) return; }

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 (Macintosh; Intel Mac OS X 10.15; rv:138.0) Gecko/20100101 Firefox/138.0

Browser/OS: Firefox 138 on Mac OS X 10.15

View result in a separate tab

for-in

139.0M/s

Object.keys

10K/s

View exact numbers

Test name	Executions per second
✓ for-in	139,039,056 Ops/sec
Object.keys	10,298 Ops/sec

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

LLMs can make mistakes. Check important info.

The benchmark named "for-in vs object.keys for checking empty" evaluates the performance of two different methods for determining whether an object is empty in JavaScript: using a `for...in` loop and utilizing the `Object.keys()` method.

### Options Compared
1. **Using `for...in` Loop**:
   - **Code Example**: 
     ```javascript
     for (var key in obj) {
         if (key) return;
     }
     ```
   - **Test Name**: "for-in"

2. **Using `Object.keys()` Method**:
   - **Code Example**: 
     ```javascript
     if (!Object.keys(obj).length) return;
     ```
   - **Test Name**: "Object.keys"

### Pros and Cons

#### 1. For-in Loop
- **Pros**:
  - **Performance**: As indicated by the benchmark results, this method is significantly faster. In the provided results, it executed approximately **139 million times** per second.
  - **Simplicity**: It uses less syntax and directly checks property existence.
  
- **Cons**:
  - **Prototype Chain**: It iterates over all enumerable properties, including those inherited from the prototype chain, which could lead to unexpected results if the object has inherited properties.
  - **Can be Misleading**: If the object has additional properties, it won't correctly determine if the object is empty.

#### 2. Object.keys() Method
- **Pros**:
  - **Accuracy**: This method creates an array of keys from the object itself, excluding inherited properties, which makes it a more reliable approach to checking if an object is empty.
  - **Readability**: The code can be clearer in expressing the intent, making it easier for other developers to understand.

- **Cons**:
  - **Performance**: It performs slower (about **10 thousand times** per second in this benchmark) due to the overhead of creating a keys array and measuring its length.
  - **Memory Usage**: The creation of an array can increase memory usage, especially with larger objects.

### Comparison and Other Considerations
When considering which approach to use, developers should evaluate their specific use case. For performance-critical applications, particularly where the check might happen frequently, the `for...in` loop could be more suitable, but they should ensure that the objects being checked do not inherit properties from other prototypes. Alternatively, if correctness is paramount—especially in cases where the object may inherit properties—the `Object.keys()` function is safer despite its performance drawbacks.

### Alternatives
Other alternatives to check if an object is empty include:
- **Object.entries()**: Similar to `Object.keys()`, it can be used to check the length of key-value pairs. However, like `Object.keys()`, this approach is less efficient and still includes the overhead of creating an array.
  
- **JSON.stringify()**: Converting the object to a JSON string and checking if it equals `{}` can also indicate emptiness, though this is inefficient for performance.

- **`Reflect.ownKeys()`**: Useful for checking all keys (including non-enumerable properties), but similarly suffers from performance costs.

Choosing the right method depends on weighing performance against accuracy and clarity, depending on the context in which the check is performed.

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

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

Created: one year ago by: Guest

Go 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):

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

Comparing performance of: for-in vs Object.keys

Created: one year ago by: Guest

Go 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):

Related benchmarks

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