Benchmark: for-in vs object.keys vs object.values for objects test

Script Preparation code:

var obj = {
  'a': {
    id: 'a',
    num: 1
  },
  'b': {
    id: 'b',
    num: 1
  },
  'c': {
    id: 'c',
    num: 1
  },
  'd': {
    id: 'd',
    num: 1
  },
  'e': {
    id: 'e',
    num: 1
  },
  'f': {
    id: 'f',
    num: 1
  },
  'g': {
    id: 'g',
    num: 1
  },
};

Tests:

for-in
for (var i=10000; i > 0; i--) { const array = [] for (var key in obj) { array.push({newid: obj[key].id}); } }
Object.keys
for (var i=10000; i > 0; i--) { const array = [] Object.keys(obj).forEach(key => array.push({newid: obj[key].id})); }
Object.values
for (var i=10000; i > 0; i--) { const array = [] Object.values(obj).forEach(n => array.push({newid: n.id})); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for-in
Object.keys
Object.values

Fastest: N/A

Slowest: N/A

Autogenerated LLM Sumamry (model llama3.2:3b, generated 2 days ago):

LLMs can make mistakes. Check important info.

**Benchmark Overview**

The provided benchmark is designed to compare the performance of three different approaches for iterating over objects in JavaScript: `for-in`, `Object.keys()`, and `Object.values()`.

**Options Compared**

* `for-in`: This approach uses the `in` operator to iterate over the object's properties. It returns an array-like object containing all property names with their corresponding values.
* `Object.keys()`: This approach uses a method of the `Object` prototype to return an array of a given object's own enumerable property names as strings.
* `Object.values()`: This approach uses a method of the `Object` prototype to return an array containing the values of all properties with enumerable string keys or symbols.

**Pros and Cons**

* `for-in`:
	+ Pros: Simple, straightforward, and widely supported. It allows iteration over both enumerable and non-enumerable properties.
	+ Cons: Can be slower due to the overhead of iterating over all properties, including non-enumerable ones.
* `Object.keys()`: 
	+ Pros: Efficient for most use cases, as it only iterates over enumerable properties. It's also a method on the `Object` prototype, making it easy to access and call.
	+ Cons: May not be suitable for iterating over non-enumerable properties or symbols.
* `Object.values()`: 
	+ Pros: Efficient for iterating over values of enumerable properties with string keys or symbols. It returns an array of values in the same order as they appear in the object.
	+ Cons: Not available in older browsers (prior to Firefox 38) due to the use of `Symbol` objects.

**Library Usage**

None of the benchmark cases use external libraries, but `Object.keys()` and `Object.values()` do rely on methods that are part of the `Object` prototype.

**Special JavaScript Features or Syntax**

There are no special features or syntax used in this benchmark. However, it's worth noting that `for-in` can also iterate over non-enumerable properties if the object has a `__proto__` property (e.g., inherited properties).

**Other Alternatives**

If you wanted to compare other approaches for iterating over objects, some alternatives could include:

* Using an array of property names and indexing into it
* Using a `forEach()` loop with a custom callback function
* Using a library like Lodash's `keyBy` or `valuesIn`
* Using a library like jQuery's `.each()`

However, these approaches are not included in the provided benchmark.

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/117.0

Browser/OS: Firefox 117 on Windows

View result in a separate tab

Test name	Executions per second
for-in	634.9 Ops/sec
Object.keys	553.1 Ops/sec
Object.values	408.3 Ops/sec

Related benchmarks:

for-in vs object.keys vs object.values for objects test (version: 0)

Comparing performance of: for-in vs Object.keys vs Object.values

Created: one year ago by: Guest

Jump to the latest result

for-in

Object.keys

Object.values

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Sumamry (model llama3.2:3b, generated 2 days ago):