Benchmark: Object keys length vs for in

Script Preparation code:

var create = 60000;
var myMap = {}
var objectToCopy = {
    myUrl: 'test',
    someUrl: 'test/11',
    otherProp: true
}

for (let i; i < create; i++) {
    myMap[i] = {
        ...objectToCopy
    }
}

Tests:

Object keys
if (Object.keys(myMap).length) { // do something }
for in
let hasProp = false; for (const prop in myMap) { hasProp = true; break; } if (hasProp) { // do something }

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: one year ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Safari/537.36

Browser/OS: Chrome 132 on Linux

View result in a separate tab

Test name	Executions per second
Object keys	113018160.0 Ops/sec
for in	142106784.0 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 JSON**

The provided JSON represents a benchmark definition for a test case named "Object keys length vs for in". This benchmark compares two approaches:

1. **Using `Object.keys()`**: The first approach uses the `Object.keys()` method to get an array of property names in the object.
2. **Using `for...in` loop**: The second approach uses a traditional `for...in` loop to iterate over the properties of the object.

**Options Compared**

The benchmark compares the performance of these two approaches:

* `Object.keys()`: This method returns an array of property names in the object, which can be used for various purposes.
* `for...in` loop: This traditional approach iterates over the properties of the object using a loop, which can be useful when you need to perform specific actions on each property.

**Pros and Cons**

Here's a brief overview of the pros and cons of each approach:

* **Using `Object.keys()`:**
	+ Pros:
		- More concise and expressive
		- Easier to read and maintain
		- Supports modern browsers
	+ Cons:
		- May not be supported in older browsers or environments
		- Can be slower due to the overhead of creating an array
* **Using `for...in` loop:**
	+ Pros:
		- More control over iteration order (if needed)
		- Supports older browsers and environments that don't support `Object.keys()`
	+ Cons:
		- Less concise and expressive
		- Requires more boilerplate code

**Library and Purpose**

There is no explicit library mentioned in the benchmark definition. However, it's worth noting that both `Object.keys()` and `for...in` loop rely on the ECMAScript specification for JavaScript objects.

**Special JS Feature or Syntax**

None of the benchmarked approaches use any special JavaScript features or syntax beyond the standard language features.

**Other Alternatives**

If you need to iterate over an object's properties, there are other alternatives:

* **Using `for...of` loop**: This is a more modern approach that iterates over an array-like object's properties using a `for...of` loop.
* **Using `Map` or `Set` objects**: Depending on the use case, you can also iterate over an object's properties by converting it to a `Map` or `Set` object.

Keep in mind that these alternatives may have different performance characteristics and trade-offs compared to the `Object.keys()` and `for...in` loop approaches.

Related benchmarks:

Object keys length vs for in (version: 0)

Comparing performance of: Object keys vs for in

Created: 2 years ago by: Registered User

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):