Benchmark: Iterate keys Object vs Map

Script Preparation code:

var object = Object.fromEntries(new Array(100000).fill(1).map((_, i) => [`key_${i}`, i]));
var map = new Map(new Array(100000).fill(1).map((_, i) => [`key_${i}`, i]));

Tests:

Iterate Object
var i = 0; for (var key in object) i += object[key];
Iterate Map
var i = 0; for (var [key, value] of map) i += value;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Iterate Object
Iterate Map

Fastest: N/A

Slowest: N/A

Latest run results:

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Autogenerated LLM Summary (model llama3.2:3b, generated one year 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 benchmark is designed to compare two approaches for iterating over an object vs. a Map in JavaScript. The main difference between the two approaches lies in how they access the key-value pairs:

1. **Object iteration**: The first approach uses the traditional `for...in` loop, which iterates over the object's own enumerable properties (key-value pairs).
2. **Map iteration**: The second approach uses the `for...of` loop with an array destructuring syntax (`[key, value] of map`), which directly accesses the key-value pairs in the Map.

**Options being compared:**

The benchmark is comparing two options:

1. Iterating over an object using the traditional `for...in` loop.
2. Iterating over a Map using the `for...of` loop with array destructuring syntax.

**Pros and Cons of each approach:**

* **Object iteration (Traditional for-in loop)**:
	+ Pros:
		- Widely supported across different browsers.
		- Familiar syntax for many developers.
	+ Cons:
		- Can be slower due to the overhead of checking property existence and iterating over the object's properties.
		- May not provide direct access to key-value pairs.
* **Map iteration (for-of loop with array destructuring)**:
	+ Pros:
		- Directly accesses key-value pairs, which can lead to better performance in some cases.
		- More concise syntax.
	+ Cons:
		- Less widely supported across different browsers. Specifically, Chrome 104's execution of this test case is slower compared to the traditional for-in loop.

**Other considerations:**

* **Library usage:** The benchmark uses the `Object.fromEntries()` and `Map` constructors, which are part of the JavaScript standard library.
* **Special JS feature or syntax:** This benchmark doesn't use any special JavaScript features or syntax. It only leverages built-in constructs (for...in loop for objects and for-of loop with array destructuring for Maps).

**Alternative approaches:**

In addition to these two main options, you might also consider exploring other iteration methods, such as:

* Using `Object.keys()` and the `forEach()` method.
* Utilizing libraries like Lodash or Ramda for functional programming.
* Employing a custom iterator implementation.

However, these alternatives might not be directly comparable to the traditional for-in loop and for-of loop with array destructuring approaches used in this benchmark.

Related benchmarks:

Iterate keys Object vs Map (version: 0)

Comparing performance of: Iterate Object vs Iterate Map

Created: 3 years ago by: Guest

Jump to the latest result

Iterate Object

Iterate Map

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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