Benchmark: for in break vs object keys

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]; console.log(output); break; }
Object keys
let output; output = Object.values(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

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

**What is being tested?**

The provided JSON represents two JavaScript microbenchmarks, "for in break vs object keys", which test the performance difference between using a traditional `for...in` loop with a `break` statement and accessing an object's values directly using the `Object.keys()` method.

**Options compared:**

Two approaches are being compared:

1. **Traditional `for...in` loop with `break`:**
	* This approach iterates over the object's properties using `for...in`, which returns both own enumerable and non-enumerable properties, including inherited ones.
	* The loop breaks early when a certain condition is met, reducing unnecessary iterations.
2. **Accessing object values directly using `Object.keys()`:**
	* This approach uses the `Object.keys()` method to get an array of the object's own enumerable property names.
	* It then iterates over this array, accessing each value using bracket notation (`testObj[key]`).

**Pros and cons of each approach:**

1. **Traditional `for...in` loop with `break`:**
	* Pros:
		+ Often faster due to reduced overhead of iterating over an array.
		+ Can be more efficient when dealing with large objects or arrays, as it avoids the need for extra memory allocation and copying.
	* Cons:
		+ May not work correctly if the object has non-enumerable properties or inherited ones, which can lead to unexpected behavior.
		+ Requires manual management of the loop's termination condition, adding complexity.
2. **Accessing object values directly using `Object.keys()`:**
	* Pros:
		+ More predictable and safer, as it only returns enumerable property names and avoids non-enumerable properties or inherited ones.
		+ Less error-prone, as the order of iteration is guaranteed by the specification.
	* Cons:
		+ May be slower due to the overhead of creating an array from the object's property names.
		+ Requires using extra memory for the array, which can be a concern in very memory-constrained environments.

**Library used:**

None explicitly mentioned. The `Object.keys()` method is a built-in JavaScript function that does not rely on any external libraries.

**Special JS feature/syntax:**

None mentioned.

**Other alternatives:**

If you need to compare the performance of accessing an object's values using different methods, consider these additional approaches:

1. **Using `for...of` loop:** This approach iterates over the array-like properties of the object using a `for...of` loop, which provides a more modern and concise way to iterate over arrays.
2. **Using `Object.values()` method:** Similar to `Object.keys()`, but returns an array containing all values of an object's own enumerable properties.
3. **Using `Array.prototype.forEach()` or `Array.prototype.reduce()` methods:** These approaches can be used to iterate over the object's property names and values, providing more control over the iteration process.

When choosing between these alternatives, consider your specific use case, performance requirements, and personal preference for syntax and semantics.

Related benchmarks:

for in break vs object keys (version: 0)

Comparing performance of: for in break vs Object keys

Created: 5 years ago by: Guest

Jump to the latest result

for in break

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):