Benchmark: Object.keys().length vs Map.size

Script Preparation code:

var data = new Array(100000).fill(undefined).map((_,i) => i)
var obj = data.reduce((obj, idx) => {obj['idx' + idx] = idx; return obj}, {});
var map = new Map(Object.entries(obj));

Tests:

Object.keys().length
var size = Object.keys(obj).length
Map.size
var size = map.length

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.keys().length
Map.size

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Firefox/102.0

Browser/OS: Firefox 102 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
Object.keys().length	877.3 Ops/sec
Map.size	868779136.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases to understand what's being tested.

**Benchmark Definition**

The website provides a JSON object that defines a benchmark, which includes:

* `Name`: The name of the benchmark, "Object.keys().length vs Map.size".
* `Description`: An empty description, suggesting that no specific functionality is being measured.
* `Script Preparation Code`:
	+ Creates an array `data` with 100,000 elements filled with `undefined`.
	+ Maps over the data using the `map()` method to generate an index for each element, and then uses the `reduce()` method to create a JavaScript object (`obj`) where each property is indexed by its corresponding value.
	+ Creates a new Map (`map`) from the object's entries.
* `Html Preparation Code`: Empty, indicating that no HTML setup is required.

The script preparation code generates an object with 100,000 properties, which are then used to create both an object using the `Object.keys()` method and a Map using the `Map.size` property. The goal of this benchmark is likely to compare the performance of these two approaches for accessing and querying the size of an object.

**Individual Test Cases**

There are two test cases:

1. **"Object.keys().length"`:
	* Benchmark Definition: `var size = Object.keys(obj).length`
	* This test case measures the performance of using the `Object.keys()` method to get the length of the object.
2. **"Map.size"`:
	* Benchmark Definition: `var size = map.length`
	* This test case measures the performance of using the `Map.size` property to get the size of the Map.

**Library and Special JS Features**

Both test cases use built-in JavaScript methods:

* `Object.keys()` is a method of the `Object` object, which returns an array of a given object's own enumerable property names.
* `Map.size` is a property of the `Map` object, which returns the number of key-value pairs in the Map.

**Pros and Cons**

Here are some pros and cons for each approach:

1. **"Object.keys().length"`:
	+ Pros: Widely supported across browsers and platforms; easy to use.
	* Cons: May be slower than using `Map.size` due to the overhead of iterating over property names.
2. **"Map.size"`:
	+ Pros: Can be faster than using `Object.keys()` since it directly returns the size, without iteration.
	* Cons: May not work in older browsers or environments that don't support Maps.

**Other Considerations**

When choosing between these two approaches, consider the following:

* If you need to iterate over an object's properties for some reason (e.g., finding specific values), `Object.keys()` might be a better choice. However, this comes at the cost of potentially slower performance.
* If you're working with large datasets and want to minimize overhead, `Map.size` is likely a better option.

**Alternatives**

Other alternatives to consider for accessing an object's size or size of a Map include:

* Using `Object.entries()` and then getting the length of the resulting array (similar to `Object.keys()`)
* Implementing your own custom method to get the size (e.g., by counting properties manually)
* Using a library like Lodash, which provides the `size` function for objects and Maps.

Related benchmarks:

Object.keys().length vs Map.size (version: 0)

Comparing performance of: Object.keys().length vs Map.size

Created: 2 years ago by: Registered User

Jump to the latest result

Object.keys().length

Map.size

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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