Benchmark: For in vs Object.*.forEach vs Object.values vs Object.entries in for loop

Script Preparation code:

var obj = new Object()
var keys = (new Array(10000)).fill(0).map((x, i) => { return i + 1 })
keys.forEach((x) => { obj['prop' + x] = x })

Tests:

For In
for (var key in obj) { console.log(obj[key]); }
Object values
for(let value of Object.values(obj)){ console.log(value); }
Object keys forEach
Object.keys(obj).forEach(key => console.log(obj[key]));
Object entries forEach
Object.entries(obj).forEach(([key, value]) => console.log(key,'->',value));
object values forEach
Object.values(obj).forEach(value => console.log(value));
Object entries plus for loop
let entries = Object.entries(obj) let length = entries.length for(let i = 0; i < length; i++){ console.log(entries[i][1]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For In
Object values
Object keys forEach
Object entries forEach
object values forEach
Object entries plus for loop

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

**Benchmark Overview**

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks. The provided JSON represents a benchmark test case, which compares the performance of different approaches for iterating over an object in a loop.

**Benchmark Definition**

The benchmark definition defines two main variables:

* `obj`: an empty object created using the `Object()` constructor.
* `keys`: an array of 10,000 numbers generated using the `fill()` and `map()` methods.

The script preparation code initializes the `obj` variable and populates it with properties using the `forEach()` method. The `keys` array is then populated with values from 1 to 10,000.

**Comparison Options**

The benchmark test case compares six different approaches for iterating over the object in a loop:

1. **For In**: uses the `for...in` loop syntax to iterate over the object's properties.
2. **Object values**: uses the `Object.values()` method to get an array of the object's values.
3. **Object keys forEach**: uses the `Object.keys()` method and the `forEach()` method to iterate over the object's keys.
4. **Object entries forEach**: uses the `Object.entries()` method and the `forEach()` method to iterate over the object's key-value pairs.
5. **Object values forEach**: uses the `Object.values()` method and the `forEach()` method to iterate over the object's values.
6. **Object entries plus for loop**: uses the `Object.entries()` method to get an array of the object's key-value pairs, and then iterates over the array using a traditional `for` loop.

**Pros and Cons**

Here are some pros and cons for each approach:

1. **For In**:
	* Pros: simple and straightforward, no extra dependencies required.
	* Cons: slower due to the overhead of iterating over properties using `for...in`.
2. **Object values**:
	* Pros: efficient and concise, leverages built-in method.
	* Cons: requires a new array object creation, which can be memory-intensive.
3. **Object keys forEach**:
	* Pros: efficient and concise, leverages built-in method.
	* Cons: only iterates over keys, not values or key-value pairs.
4. **Object entries forEach**:
	* Pros: efficient and concise, leverages built-in method.
	* Cons: requires a new array object creation, which can be memory-intensive.
5. **Object values forEach**:
	* Pros: similar to `Object.values()` with added iteration logic.
	* Cons: requires an extra function call and creates a new array object.
6. **Object entries plus for loop**:
	* Pros: flexible and customizable, no dependencies required.
	* Cons: more verbose and error-prone due to manual iteration.

**Library Use**

The benchmark test case uses the following libraries:

1. `Array.prototype.fill()`: fills an array with a specified value.
2. `Array.prototype.map()`: applies a function to each element of an array.
3. `Object.keys()`: returns an array of the object's keys.
4. `Object.values()`: returns an array of the object's values.
5. `Object.entries()`: returns an array of the object's key-value pairs.

**Special JavaScript Features or Syntax**

None of the benchmark test cases use special JavaScript features or syntax that are not widely supported.

**Alternative Approaches**

Other approaches for iterating over objects in a loop include:

1. Using `for...of` loops with `Object.entries()` or `Object.values()`.
2. Using traditional `for` loops and accessing properties directly using bracket notation.
3. Using arrow functions and the `forEach()` method on arrays of keys or values.

These alternative approaches may offer different trade-offs in terms of performance, conciseness, and readability, depending on the specific use case and requirements.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/129.0.0.0 Safari/537.36

Browser/OS: Chrome 129 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
For In	41.1 Ops/sec
Object values	41.4 Ops/sec
Object keys forEach	42.3 Ops/sec
Object entries forEach	32.2 Ops/sec
object values forEach	40.1 Ops/sec
Object entries plus for loop	37.0 Ops/sec

Related benchmarks:

For in vs Object.*.forEach vs Object.values vs Object.entries in for loop (version: 0)

Comparing performance of: For In vs Object values vs Object keys forEach vs Object entries forEach vs object values forEach vs Object entries plus for loop

Created: one year ago by: Guest

Jump to the latest result

For In

Object values

Object keys forEach

Object entries forEach

object values forEach

Object entries plus for loop

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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