Benchmark: for-in vs object.keys Test2

Script Preparation code:

var obj = {
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
};

Tests:

for-in
var array = []; for (var key in obj) { array.push(key); } console.log("Done: ", array);
Object.keys
var array = Object.keys(obj); console.log("Done: ", array);

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:

No previous run results

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

LLMs can make mistakes. Check important info.

I'll break down what's being tested in the provided JSON and explain the different approaches, their pros and cons, and other considerations.

**Benchmark Definition**

The benchmark is testing two ways to iterate over an object: `for-in` loop and `Object.keys()` method. The script preparation code defines a large object `obj` with 26 properties (with duplicate keys).

**Script Preparation Code**
```javascript
var obj = {
    'a': 1,
    'b': 1,
    'c': 1,
    'd': 1,
    'e': 1,
    'f': 1,
    'g': 1,
    'a': 1,
    'b': 1,
    'c': 1,
    'd': 1,
    'e': 1,
    'f': 1,
    'g': 1,
    'a': 1,
    'b': 1,
    'c': 1,
    'd': 1,
    'e': 1,
    'f': 1,
    'g': 1,
    'a': 1,
    'b': 1,
    'c': 1,
    'd': 1,
    'e': 1,
    'f': 1,
    'g': 1,
    'a': 1,
    'b': 1,
    'c': 1,
    'd': 1,
    'e': 1,
    'f': 1,
    'g': 1,
    'a': 1,
    'b': 1,
    'c': 1,
    'd': 1,
    'e': 1,
    'f': 1,
    'g': 1,
};
```
**Html Preparation Code**

There is no HTML preparation code provided.

**Individual Test Cases**

The benchmark consists of two test cases:

### For-in

```javascript
for (var key in obj) {
    array.push(key);
}
console.log("Done: ", array);
```

This test case uses a traditional `for-in` loop to iterate over the object's properties and push them into an array.

### Object.keys()

```javascript
var array = Object.keys(obj);
console.log("Done: ", array);
```

This test case uses the `Object.keys()` method to get an array of the object's property names.

**Pros and Cons**

*   **For-in Loop**:

*   Pros:
        *   Easy to implement for simple iteration cases.
        *   Can handle objects with duplicate keys, as it iterates over all properties.
    *   Cons:
        *   May have performance issues due to the use of `var key` (variable hoisting), which can lead to unexpected behavior in certain scenarios.
        *   Not suitable for iterating over object's own enumerable property names only.
*   **Object.keys() Method**:

*   Pros:
        *   Faster and more efficient than the `for-in` loop, especially for large objects with many properties.
        *   Returns an array of property names, which can be iterated over using a traditional `for` loop or other array methods.
        *   Suitable for iterating over object's own enumerable property names only.
    *   Cons:
        *   May not work as expected in older browsers that do not support the `Object.keys()` method.

**Other Considerations**

*   In modern JavaScript, using `Object.keys()` is generally recommended over traditional `for-in` loops due to its efficiency and clarity.
*   When dealing with objects containing duplicate keys, the use of an array or other data structure can help resolve potential issues with duplicate values in properties that have different types.

**Alternative Approaches**

If you need to iterate over object's property names for a specific purpose (e.g., object manipulation or caching), consider using:

*   `for...in` loop: This is suitable for iterating over all enumerable properties, but may not be the best choice due to potential performance issues and unexpected behavior.
*   `Object.getOwnPropertyNames()` method: This returns an array of all property names in the given object, including non-enumerable ones. It's a good alternative when you need access to both own enumerable and non-enumerable properties.

Keep in mind that there is no universally "best" approach for iterating over objects. The choice ultimately depends on your specific use case, performance requirements, and personal preference.

Related benchmarks:

for-in vs object.keys Test2 (version: 0)

Comparing performance of: for-in vs Object.keys

Created: 6 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

No previous run results

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