Benchmark: fn field vs obj field

Script Preparation code:

var fn = () => {}
var fn2 = function fn2() {}
var obj = {}

Tests:

fn
fn.a = 'a'
fn2
fn2.a = 'a'
obj
obj.a = 'a'

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
fn
fn2
obj

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 17_1_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.1.2 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 17 on iOS 17.1.2

View result in a separate tab

Test name	Executions per second
fn	33114060.0 Ops/sec
fn2	36465088.0 Ops/sec
obj	33703032.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON and explain what's being tested, compared, and some considerations.

**Benchmark Definition**

The provided benchmark definition is simple: it tests the performance difference between accessing fields using a function (`fn`) versus an object (`obj`). The code prepares two functions, `fn` and `fn2`, which are assigned to a property `a`. Another object, `obj`, is also created.

**Test Cases**

There are three test cases:

1. `fn.a = 'a'`: Tests accessing the field `a` using the function `fn`.
2. `fn2.a = 'a'`: Tests accessing the field `a` using the function `fn2`.
3. `obj.a = 'a'`: Tests accessing the field `a` using the object `obj`.

**Comparison**

The test is comparing the performance of accessing a field using a function versus an object. In JavaScript, when you access a property on an object using a dot notation (e.g., `obj.a`), it creates a new accessor function if the property doesn't exist. However, when you use a function to access a property (e.g., `fn.a`), it uses a different optimization mechanism.

**Pros and Cons**

Using functions to access fields can provide some performance benefits:

* **Cache hits**: When using functions, the V8 JavaScript engine (used by Chrome) can cache the results of previous executions, which can lead to faster subsequent calls. This is known as "cache hit".
* **Less overhead**: Functions require less overhead than objects when accessing properties.

However, there are also some potential drawbacks:

* **Overhead for function creation**: While functions have less overhead than objects, creating a new function still involves some overhead.
* **Potential caching issues**: If the function is not properly memoized, it may not take advantage of cache hits.

Using objects to access fields has its own set of considerations:

* **Native object optimizations**: When using native objects (e.g., built-in arrays or strings), JavaScript engines can optimize these accesses more effectively.
* **Less control over caching**: With objects, the V8 engine may not be able to cache results as effectively, leading to slower performance.

**Library and Special Features**

There is no library used in this benchmark. However, some notes on special features:

* **Arrow functions**: The use of arrow functions (`=>`) in `fn` can provide additional benefits, such as avoiding the overhead of function declaration.
* **Function expressions**: The use of function expressions (`var fn = () => {}`) can also lead to performance improvements.

**Other Alternatives**

If you're interested in exploring alternative approaches, here are a few options:

* **Native array or string accesses**: Using built-in arrays or strings and accessing elements using indexing (e.g., `arr[0]` or `str[1]`) can provide faster performance.
* **Built-in methods**: Utilizing built-in methods like `Object.hasOwn()` or `Array.prototype.indexOf()`, which are optimized for their respective use cases, can also lead to better performance.

Keep in mind that the V8 JavaScript engine is highly optimized for native object accesses and function calls. While exploring alternative approaches can be interesting, it's essential to consider the context and specific requirements of your project before investing time and resources into optimizing these scenarios.

Related benchmarks:

fn field vs obj field (version: 0)

Comparing performance of: fn vs fn2 vs obj

Created: 2 years ago by: Registered User

Jump to the latest result

fn

fn2

obj

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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