Benchmark: let and return vs IIFE

HTML Preparation code:

<a id='test' href='#' />

Script Preparation code:

el=document.querySelector("#test");
isInViewportLet=e=>{
  let r;
  return (r=e.getBoundingClientRect(),
          0 <= r.y &&
          0 <= r.x &&
          r.bottom <= innerHeight &&
          r.right <= innerWidth &&
          r.y < r.bottom &&
          r.x < r.right
         )
};
isInViewportIIFE=e=>(
  (r=>(
    0 <= r.y &&
    0 <= r.x &&
    r.bottom <= innerHeight &&
    r.right <= innerWidth &&
    r.y < r.bottom &&
    r.x < r.right
  ))(e.getBoundingClientRect())
);

Tests:

let and return
isInViewportLet(el);
IIFE
isInViewportIIFE(el);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
let and return
IIFE

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Mobile Safari/537.36

Browser/OS: Chrome Mobile 120 on Android

View result in a separate tab

Test name	Executions per second
let and return	73432.2 Ops/sec
IIFE	76213.9 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks.

**Benchmark Description**

The `MeasureThat.net` benchmark compares the performance of two approaches to check if an element is within the viewport: using a traditional `let` and `return` statement, and using an Immediately Invoked Function Expression (IIFE).

**Options Compared**

Two options are compared:

1. **Traditional `let` and `return`**: This approach uses a traditional block scope to declare variables, which can lead to slower performance due to the overhead of scoping.
2. **Immediately Invoked Function Expression (IIFE)**: This approach uses an IIFE to create a new scope, which can provide faster performance by avoiding the overhead of scoping.

**Pros and Cons**

* **Traditional `let` and `return`**:
	+ Pros: Easier to read and understand for developers familiar with traditional JavaScript.
	+ Cons: Can lead to slower performance due to scoping overhead.
* **IIFE**:
	+ Pros: Can provide faster performance by avoiding scoping overhead.
	+ Cons: May be less readable and more difficult to understand for developers unfamiliar with IIFEs.

**Library Usage**

The `isInViewport` function uses the `getBoundingClientRect()` method, which is a part of the W3C DOM standard. This method returns an object representing the element's bounding rectangle, which contains information about its position and size relative to the viewport.

**Special JS Feature/Syntax**

There is no special JavaScript feature or syntax used in this benchmark. The code uses only standard JavaScript features and syntax.

**Other Considerations**

When writing performance-critical code, it's essential to consider the following:

* Use modern JavaScript features and syntax whenever possible.
* Minimize the use of scoping mechanisms like `let` and `return`.
* Use IIFEs or other scope-creating techniques judiciously to optimize performance.

**Alternative Approaches**

If you need to check if an element is within the viewport, you can consider using alternative approaches:

1. **Use a library**: Libraries like jQuery or React provide built-in functions for checking element visibility and position.
2. **Use a CSS-based solution**: You can use CSS to position elements in a way that makes them visible only when they are within the viewport.
3. **Optimize DOM manipulation**: If you need to frequently update the visibility of elements, consider optimizing your DOM manipulation code using techniques like batch updates or lazy loading.

In conclusion, the `MeasureThat.net` benchmark provides valuable insights into the performance differences between traditional `let` and `return` statements versus IIFEs in JavaScript. By understanding these differences, developers can make informed decisions about which approach to use in their own performance-critical code.

Related benchmarks:

let and return vs IIFE (version: 0)

Designed to measure the performance of a workaround where an IIFE is used to eliminate let and return statements, which makes the function shorter.

Comparing performance of: let and return vs IIFE

Created: 2 years ago by: Registered User

Jump to the latest result

let and return

IIFE

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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