Benchmark: for in vs for of

Script Preparation code:

var basicRoom = {a: 1, b: 2, c: 3};
var obj = {N0E0: basicRoom, N1E2: basicRoom, S1E3: basicRoom, S4E4: basicRoom, N5W3: basicRoom, S22W45: basicRoom, N40W20: basicRoom, N15E15: basicRoom, S15W15: basicRoom};

Tests:

for in
for (var x in obj) { console.log(x); }
for of
for (var x of Object.keys(obj)) { console.log(x); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for in
for of

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 JavaScript microbenchmark on MeasureThat.net.

**Benchmark Definition and Script Preparation Code**

The benchmark is comparing two approaches for iterating over an object: `for in` and `for of`. The script preparation code defines an object `obj` with multiple properties, each containing a reference to another object or string. This allows us to test the performance of different iteration methods.

**Options Compared**

The benchmark is comparing the following options:

1. **For In Loop (`for (var x in obj)`):**
	* Iterates over the object's properties using the `in` operator.
	* May have issues with property names containing special characters or non-ASCII characters, as they may not be properly encoded.
	* Can be slower due to the overhead of checking if each property is present in the object.
2. **For Of Loop (`for (var x of Object.keys(obj))`):**
	* Iterates over an array of property names obtained from `Object.keys(obj)`.
	* Uses a more modern and efficient approach, as it relies on the built-in `keys()` method and array iteration.

**Pros and Cons**

1. **For In Loop:**
	* Pros:
		+ More readable and familiar syntax for many developers.
		+ Works well with objects that have a small number of properties.
	* Cons:
		+ Can be slower due to the overhead of checking if each property is present in the object.
		+ May not work correctly with objects that have special characters or non-ASCII characters in their property names.
2. **For Of Loop:**
	* Pros:
		+ More efficient and faster, as it relies on built-in methods and array iteration.
		+ Works well with objects of any size.
	* Cons:
		+ Requires modern browsers that support the `Object.keys()` method and `for...of` loop syntax.

**Libraries and Special Features**

There are no libraries used in this benchmark. However, it's worth noting that the `for...of` loop syntax was introduced in ECMAScript 2015 (ES6) and is supported by modern browsers.

**Other Alternatives**

For iterating over objects, other approaches can be considered:

1. **Using a `forEach()` method:** This approach uses the built-in `forEach()` method on the object itself, which can be faster than using a `for...in` loop.
```javascript
obj.forEach(function(property) {
  console.log(property);
});
```
2. **Using an iterator or a custom iterator function:** This approach creates an iterator that yields each property name in the object, allowing for more control over the iteration process.

In conclusion, the benchmark is comparing two popular approaches for iterating over objects: `for in` and `for of`. While both methods have their pros and cons, the `for of` loop syntax is generally faster and more efficient due to its reliance on built-in methods and array iteration.

Related benchmarks:

for in vs for of (version: 0)

Comparing performance of: for in vs for of

Created: 9 years ago by: Guest

Jump to the latest result

for in

for of

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):