Benchmark: for in break vs object keys really better

Script Preparation code:

var testObj = {}
for (let i = 0; i < 10000; i++) {
  const randomString = Math.random().toString(36).substr(2, 5);
  testObj[randomString] = randomString;
}

Tests:

for in break
let output; for (const key in testObj) { output = testObj[key]; break; } console.log(output);
Object keys
let output; output = Object.values(testObj)[0]; console.log(output);
Object keys for real
let output; output = testObj[Object.keys(testObj)[0]]; console.log(output);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for in break
Object keys
Object keys for real

Fastest: N/A

Slowest: N/A

Latest run results:

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

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Let's break down the benchmark and its various components.

**Benchmark Definition**

The benchmark is defined in JSON format, which represents a script that will be executed to test performance. The script preparation code creates an object `testObj` with 10,000 properties, each initialized with a random string.

There are three different approaches being tested:

1. **For-in loop with break**: This approach uses a traditional for-in loop to iterate over the object's keys, and breaks out of the loop as soon as it finds a match.
2. **Object.keys()**: This approach uses the `Object.keys()` method to get an array of the object's keys, and then accesses the first key in the array to retrieve its corresponding value.
3. **Object keys with indexing**: This approach uses the same approach as the previous one, but instead of accessing the first key directly, it uses the index of the first key in the `Object.keys()` result.

**Options compared**

The three approaches are being compared to determine which one is the most efficient.

**Pros and Cons**

Here's a brief summary of each approach:

1. **For-in loop with break**:
	* Pros: Simple, straightforward approach that works well for small objects.
	* Cons: Can be slow due to the need to check if a key has already been broken out of.
2. **Object.keys()**:
	* Pros: Fast and efficient, as it uses an optimized internal loop to iterate over the keys.
	* Cons: May require more memory, as it creates an array of all keys.
3. **Object keys with indexing**:
	* Pros: Similar performance to Object.keys(), but avoids creating an array of all keys.
	* Cons: Requires accessing the first key in the `Object.keys()` result, which may be slower for large objects.

**Library**

None of the approaches rely on any external libraries.

**Special JS features or syntax**

There is no special JavaScript feature or syntax being used in this benchmark. All three approaches use standard JavaScript syntax and features.

**Other alternatives**

If you wanted to test other approaches, you could consider using:

* **Array.prototype.forEach()**: This method can be used as an alternative to the for-in loop.
* **Object.values()**: This method returns an array of all values in the object, similar to Object.keys(), but without the keys.
* **Enum-based loops**: Some older browsers may support enum-based loops, which could be another approach to iterate over object keys.

Overall, this benchmark is designed to test the performance of three different approaches to iterating over an object's keys. The results can help developers and browser maintainers optimize their JavaScript implementations for better performance.

Related benchmarks:

for in break vs object keys really better (version: 0)

Comparing performance of: for in break vs Object keys vs Object keys for real

Created: 5 years ago by: Guest

Jump to the latest result

for in break

Object keys

Object keys for real

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):