Benchmark: Object iteration vs Map iteration with deep cloning

Script Preparation code:

var obj = {
  a: 1,
  b: 2,
  c: 3,
  d: 4,
  e: 5,
  f: 6,
  g: 7,
  h: 8,
  i: 9,
  j: 10,
  k: 11,
  l: 12,
  m: 13,
  n: 14,
  o: 15,
  p: 16,
  q: 17,
  r: 18,
  s: 19,
  t: 20,
  u: 21,
  v: 22,
  w: 23,
  x: 24,
  y: 25,
  z: 26
};
var map = new Map(Object.entries(obj));

Tests:

Map - for of kv
let total = 0; const newMap = new Map(map); for (const [key, value] of newMap) { total += value; }
Object.entries() - for of kv
let total = 0; const newObj = {...obj} for (const [key, value] of Object.entries(newObj)) { total += value; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Map - for of kv
Object.entries() - for of kv

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 Description**

The provided JSON represents two JavaScript microbenchmarks that test the performance difference between iterating over an object using `Object.entries()` and iterating over a Map using the `for...of` loop.

**Options Compared**

There are two options compared:

1. **Object.entries() - for of kv**: This option iterates over the entries of the original object (`obj`) using `Object.entries()`, which returns an array of key-value pairs, and then uses a `for...of` loop to iterate over these entries.
2. **Map - for of kv**: This option creates a new Map from the original object's entries (using `new Map(Object.entries(obj))`) and then iterates over its entries using a `for...of` loop.

**Pros and Cons**

* **Object.entries() - for of kv**:
	+ Pros: This approach can be more straightforward to implement, as it only requires iterating over the object's properties.
	+ Cons: The `Object.entries()` method creates a new array, which may incur additional overhead due to memory allocation and copying. Additionally, this approach does not take advantage of Map's internal implementation optimizations.
* **Map - for of kv**:
	+ Pros: This approach leverages the optimized iteration mechanism provided by Maps in JavaScript, which can result in faster execution times.
	+ Cons: Creating a new Map object may incur additional overhead due to memory allocation and copying.

**Library Used**

In both test cases, the `Map` data structure is used. The `Map` class represents an ordered collection of key-value pairs that are stored as separate entries, with each entry consisting of a key and a value.

The `Object.entries()` method is also part of the standard JavaScript object model, but it's worth noting that this approach relies on the underlying implementation details of objects in JavaScript.

**Special JS Feature or Syntax**

Neither of these test cases uses any special JavaScript features or syntax. They only rely on standard language constructs and built-in data structures (Map and Object).

**Other Considerations**

When considering benchmarking microbenchmarks, it's essential to consider factors such as:

* **Memory allocation**: Creating new objects or arrays can incur additional overhead due to memory allocation.
* **Cache performance**: The cache hierarchy in modern CPUs plays a significant role in determining performance. Iterating over large datasets can lead to poor cache locality, which can negatively impact performance.
* **CPU instructions**: Modern CPUs have optimized instructions for iterating over collections, such as the `for...of` loop and Map iteration.

**Alternatives**

Other alternatives for benchmarking JavaScript microbenchmarks include:

* Using other data structures, such as arrays or sets.
* Incorporating additional complexity to the benchmark, like recursion or function calls.
* Leveraging WebAssembly or other just-in-time (JIT) compilation techniques.
* Using different programming languages or frameworks.

However, these alternatives may not be directly comparable to the provided benchmarks, as they introduce varying degrees of complexity and overhead.

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36

Browser/OS: Chrome 114 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Map - for of kv	825691.9 Ops/sec
Object.entries() - for of kv	1338234.1 Ops/sec

Related benchmarks:

Object iteration vs Map iteration with deep cloning (version: 0)

Comparing performance of: Map - for of kv vs Object.entries() - for of kv

Created: one year ago by: Guest

Jump to the latest result

Map - for of kv

Object.entries() - for of kv

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):