Benchmark: for...of Object.keys vs for...of Object.keys.keys

Script Preparation code:

let obj = {
        a: 1,
        b: [],
        c: 'abc',
        d: Symbol('test')
    },
    keys1 = Object.keys(obj),
    keys2 = keys1.keys()

Tests:

...of Object.keys
for (let prop of keys1) console.log(prop)
...of Object.keys.keys
for (let prop of keys2) console.log(prop)

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
...of Object.keys
...of Object.keys.keys

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 22 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
...of Object.keys	8374.1 Ops/sec
...of Object.keys.keys	31187888.0 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated 22 days ago):

LLMs can make mistakes. Check important info.

The benchmark being tested is the performance of two different patterns for iterating over object keys in JavaScript. Specifically, it compares the traditional `for...of` loop used with the `Object.keys()` method versus a more unconventional approach using `Object.keys().keys()`, which is not a standard feature of JavaScript objects. Here's a breakdown of the individual components:

### Options Compared:

1. **`for...of Object.keys(obj)`**
   - Test Name: `...of Object.keys`
   - This method gets the keys of an object using `Object.keys(obj)`, which returns an array of the object's own property keys. The `for...of` loop iterates through each key, which can then be used within the loop body (in this case, to log each key to the console).

2. **`for...of keys1.keys()`**
   - Test Name: `...of Object.keys.keys`
   - This approach is unconventional. It tries to apply the `keys()` method on an array (`keys1`, which is an array of keys returned by `Object.keys()`). However, `Array.prototype.keys()` returns an iterator for the keys of the array, which is not the same as the object keys. Each call to `keys()` returns an iterator that produces the index as the property key (0, 1, 2, etc.) when iterated over, rather than the actual object keys.

### Pros and Cons:

1. **Using `for...of Object.keys(obj)`**
   - **Pros:**
     - Clear intention: Everyone familiar with JavaScript will understand that it retrieves object keys explicitly.
     - Directly gives access to the actual keys of the object.
   - **Cons:**
     - Performance may vary based on the number of properties in the object, but generally it's efficient for most use cases.

2. **Using `for...of keys1.keys()`**
   - **Pros:**
     - Innovative approach that showcases the `keys()` method of an array, which can be a useful feature in contexts where the array indices are needed.
   - **Cons:**
     - Misleading: Users might misunderstand what is being iterated over and will log numerical indices rather than the intended object keys.
     - Poor performance: With a significant overhead since the keys are not relevant to the object keys being worked with.

### Other Considerations:

- **Performance Implications:** The benchmark results show a considerable difference in performance, with the `for...of Object.keys()` yielding around 8,374 executions per second, while the `for...of keys1.keys()` yielded approximately 31,187,888 executions per second. This means that although the `keys().keys()` approach seems faster in terms of raw numbers, it doesn't give meaningful results if you consider the actual data being processed.

- **JS Feature/Browsers:** This benchmark specifically targets the behavior of the `for...of` loop and key extraction methods available in JavaScript. The `keys()` method is part of the Array prototype that returns a new array iterator object that contains the keys for each index in the array—a feature familiar to most JavaScript developers.

### Alternatives:

- **`forEach`:** Instead of using `for...of`, you could use the `forEach` method to iterate over the array of keys returned by `Object.keys()`. This is more declarative and often preferable for readability.

- **`for (var key in obj)`:** Using a `for...in` loop could be an alternative for iterating over object properties. However, this method iterates over all enumerable properties in the object, including properties from the prototype chain, which could lead to unintended behavior.

- **Using modern methods like `.map()` or other functional programming techniques can also provide cleaner and often more efficient iterations depending on the context.**

In conclusion, while the benchmark seeks to show performance differences between two approaches, the use of `Object.keys().keys()` appears more misleading than productive. The first method is more straightforward and typically the preferred way to access the keys of an object for most use cases.

Related benchmarks:

for...of Object.keys vs for...of Object.keys.keys (version: 1)

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

Created: 22 days ago by: Guest

Jump to the latest result

...of Object.keys

...of 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 22 days ago):