Benchmark: Fastest way to check if object is empty (for in vs.

Script Preparation code:

var xxx = Math.random() > 0.5 ? {foo: 'bar', hello: 'world'} : {}

Tests:

object.keys()
return Object.keys(xxx) === 0
for in
for (let key in xxx) { if (xxx.hasOwnProperty(key)) return false; } return true;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
object.keys()
for in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 8 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/139.0.0.0 Safari/537.36

Browser/OS: Chrome 139 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
object.keys()	135910912.0 Ops/sec
for in	147493520.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition and Script Preparation Code**

The benchmark is designed to measure the performance difference between two approaches: using the `for...in` loop versus the `Object.keys()` method. The script preparation code creates a random object with either 0 or 1 property, ensuring that the test cases cover both scenarios.

```javascript
var xxx = Math.random() > 0.5 ? {foo: 'bar', hello: 'world'} : {};
```

This line of code creates an object `xxx` that may have one of two possible structures:

* If `Math.random()` returns a value greater than 0.5, `xxx` is an object with two properties (`foo` and `hello`) containing strings.
* Otherwise, `xxx` is an empty object `{}`.

**Individual Test Cases**

There are two test cases:

1. **object.keys()**
```javascript
return Object.keys(xxx) === 0;
```
This test case uses the `Object.keys()` method to check if the length of the `xxx` object's property array is 0, indicating an empty object.

2. **for...in**
```javascript
for (let key in xxx) { if (xxx.hasOwnProperty(key)) return false; } return true;
```
This test case uses a traditional `for...in` loop to iterate over the properties of the `xxx` object. If any property is found using `hasOwnProperty()`, the loop exits, and the function returns `false`. If no properties are found after checking all properties, the function returns `true`, indicating an empty object.

**Comparing Options**

The two test cases compare the performance of:

1. **object.keys()**: A modern JavaScript method that returns an array-like object containing the property names of an object.
2. **for...in**: A traditional loop-based approach to iterate over an object's properties.

**Pros and Cons:**

* **object.keys():**
	+ Pros:
		- Efficient and concise way to check if an object is empty.
		- Works with modern JavaScript engines.
	+ Cons:
		- May not work in older browsers or Node.js versions without the `Object.keys()` method.
* **for...in:**
	+ Pros:
		- Widely supported by older browsers and Node.js versions.
		- Can be useful for iterating over object properties in certain contexts (e.g., when the number of properties is unknown).
	+ Cons:
		- Less efficient than `object.keys()` due to the overhead of the loop and conditional checks.

**Library:**

None explicitly mentioned, but it's worth noting that `Object.keys()` has been a part of the ECMAScript standard since ECMAScript 5 (2011), while `for...in` is a legacy construct from older JavaScript versions.

**Special JS Feature/Syntax:**

No special features or syntax are used in this benchmark. The code relies solely on standard JavaScript constructs and methods.

**Alternatives:**

Other alternatives for checking if an object is empty include:

* Using the `Object.isEmpty()` method (not supported by all browsers/Node.js versions)
* Creating a proxy object that returns an empty array when accessed as a property
* Utilizing libraries like Lodash or Underscore.js, which provide utility functions for working with objects

However, these alternatives are not typically used in microbenchmarking scenarios, where the focus is on optimizing specific code paths and measuring performance differences between simple constructs.

Related benchmarks:

Fastest way to check if object is empty (for in vs. (version: 0)

You don't need to make add for loops in your test scenarios, the benchmark does it itself.

Comparing performance of: object.keys() vs for in

Created: 3 years ago by: Guest

Jump to the latest result

object.keys()

for in

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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