Benchmark: for..of, for..in, for, map, forEach

Script Preparation code:

const arr = new Array(100).fill(1);
const obj = {
    ...arr.reduce((acc, curr) => {
        acc[curr] = curr;
        return acc;
    }, {})
}

Tests:

For of
const arr = new Array(100).fill(1); for (const item of arr) { console.log(item) }
map
const arr = new Array(100).fill(1); arr.map(console.log)
forEach
const arr = new Array(100).fill(1); arr.forEach(console.log)
for in
const arr = new Array(100).fill(1); const obj = { ...arr.reduce((acc, curr) => { acc[curr] = curr; return acc; }, {}) } for (const item in obj) { console.log(obj[item]) }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For of
map
forEach
for in

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36 Edg/130.0.0.0

Browser/OS: Chrome 130 on Windows

View result in a separate tab

for in

250K/s

For of

3K/s

forEach

696/s

map

693/s

View exact numbers

Test name	Executions per second
✓ for in	249,938 Ops/sec
For of	3,295 Ops/sec
forEach	696 Ops/sec
map	693 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year 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 benchmark definition json represents a set of test cases designed to compare the performance of different JavaScript iteration methods: `for..of`, `for..in`, `for`, `map`, and `forEach`.

**Test Case Breakdown**

The individual test cases are:

1. **For of**: Iterates over an array using the `for...of` loop, logging each item to the console.
2. **Map**: Applies a callback function to each element of an array using the `map()` method, logging each result to the console.
3. **ForEach**: Applies a callback function to each element of an array using the `forEach()` method, logging each result to the console.
4. **For in**: Iterates over an object using the `for...in` loop, logging each property value to the console.

**Library Usage**

The test cases use the following libraries:

* None (no external libraries are required for these tests)

**Special JavaScript Features or Syntax**

None of the test cases rely on special JavaScript features or syntax beyond what is built-in to the language. However, it's worth noting that the `for...of` loop and the `map()` method both take advantage of modern JavaScript's iterator protocol.

**Options Comparison**

The benchmark compares different iteration methods with varying performance characteristics:

* **For..of**: Designed for iterating over arrays using a modern, concise syntax. It is generally faster than other iteration methods.
* **For in**: Iterates over objects, which can be slower than array iteration due to the overhead of property enumeration.
* **For**: A traditional loop that requires manual indexing and looping control. This method is often slower than `for...of` and `map()`.
* **Map**: Applies a transformation function to each element of an array, returning a new array with the results. It can be faster than using `forEach()` for simple transformations.

**Pros and Cons**

Here's a brief summary of the pros and cons of each iteration method:

* **For..of**:
	+ Pros: Fast, concise syntax, suitable for arrays.
	+ Cons: Limited to iterating over arrays; may not work with other iterable objects.
* **For in**:
	+ Pros: Works with both arrays and objects; simple syntax.
	+ Cons: Slower than array iteration methods; relies on property enumeration, which can be slower.
* **For**:
	+ Pros: General-purpose loop that works with any type of object.
	+ Cons: Slow due to manual indexing and looping control; verbose syntax.
* **Map**:
	+ Pros: Fast for simple transformations; returns a new array, avoiding side effects.
	+ Cons: May incur additional memory allocation overhead; requires explicit transformation function.

**Other Alternatives**

For iterating over arrays or objects, other alternatives include:

* Using `forEach()` instead of `for...of`, which is also designed for array iteration but does not provide the same level of concision as `for...of`.
* Utilizing `reduce()`, which can be used to accumulate values in an array or object using a callback function.
* Considering other libraries or frameworks that offer optimized iteration methods, such as `loople` or `iterable utilities`.

for..of, for..in, for, map, forEach (version: 0) Benchmark.js

Comparing performance of: `For of vs map vs forEach vs for in`

Created: 5 years ago by: Guest

Go to the latest result

For of

map

forEach

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):

for..of, for..in, for, map, forEach (version: 0) Benchmark.js

Comparing performance of: For of vs map vs forEach vs for in

Created: 5 years ago by: Guest

Go to the latest result

For of

map

forEach

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):

Related benchmarks

Comparing performance of: `For of vs map vs forEach vs for in`