Benchmark: forIn vs forOfEntries

HTML Preparation code:


<script src='https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js'></script>

Tests:

forIn
const obj = {a: 'a', b: 'b', c: 'c', d: 'd', e: 'e', f: 'f', g: 'g', h: 'h', i: 'i', j: 'j'}; _.forIn(obj, (val, key) => { console.log(val, key); });
forOfEntries
const obj = {a: 'a', b: 'b', c: 'c', d: 'd', e: 'e', f: 'f', g: 'g', h: 'h', i: 'i', j: 'j'}; const entries = Object.entries(obj); for ([key, val] of entries) { console.log(val, key); }
forInEntries
const obj = {a: 'a', b: 'b', c: 'c', d: 'd', e: 'e', f: 'f', g: 'g', h: 'h', i: 'i', j: 'j'}; const entries = Object.entries(obj); for ([key, val] in entries) { console.log(val, key); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forIn
forOfEntries
forInEntries

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):

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Let's break down what's being tested here.

**Benchmark Name and Description**

The benchmark is called "forIn vs forOfEntries". It compares the performance of two different ways to iterate over an object's properties in JavaScript: `for...in` loop versus using the `Object.entries()` method with a `for...of` loop.

**Test Cases**

There are three test cases:

1. **`forIn`**: This test uses a traditional `for...in` loop to iterate over an object's properties, along with the Lodash library's `_.forIn()` function to achieve similar behavior.
2. **`forOfEntries`**: This test uses a modern `for...of` loop to iterate over the result of calling `Object.entries()`, which returns an array of key-value pairs from the object.
3. **`forInEntries`**: This test is similar to `forOfEntries`, but it uses a traditional `for...in` loop instead of `for...of`. However, it incorrectly attempts to use the same syntax as `for...of`, which will not work in this context (more on that later).

**Latest Benchmark Result**

The latest benchmark result shows the execution speed (Executions Per Second) for each test case:

* `forOfEntries` runs at 3517.693359375 executions per second.
* `forInEntries` runs at 3360.0 executions per second.
* `forIn` runs at 3314.451171875 executions per second.

**Library Used**

The Lodash library is used in the test case for `forIn`. It's a popular utility library that provides various functional programming helpers, including a `_.forIn()` function that iterates over an object's properties and performs a callback function for each property.

**Special JS Feature or Syntax**

There are two special features being tested here:

* **`Object.entries()`**: This is a modern feature introduced in ECMAScript 2017 (ES8) that returns an array of key-value pairs from an object.
* **`for...of` loop**: This is a modern `for` loop syntax introduced in ES6, which allows iterating over arrays or iterable objects.

**Pros and Cons**

Here are some general pros and cons for each approach:

* `for...in` loop:
	+ Pros: simple to use, works with older JavaScript engines.
	+ Cons: may iterate over inherited properties, can be slow if the object has many properties.
* Using `Object.entries()` with `for...of` loop:
	+ Pros: efficient, easy to read, and write, doesn't iterate over inherited properties.
	+ Cons: requires modern JavaScript engine support (ES8+).

**Other Alternatives**

There are other ways to iterate over an object's properties in JavaScript:

* **`Object.keys()`**: Returns an array of keys from the object.
* **`Object.getOwnPropertyNames()`**: Returns an array of all property names, including non-enumerable ones.

Keep in mind that these alternatives might not be as efficient or convenient as using `for...of` loops with `Object.entries()`.

Related benchmarks:

forIn vs forOfEntries (version: 0)

Comparing performance of: forIn vs forOfEntries vs forInEntries

Created: 8 years ago by: Guest

Jump to the latest result

forIn

forOfEntries

forInEntries

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.1:latest, generated one year ago):