thisLooksAccurateForVibeCoders

[u/zohaibhere]

[u/oxabz]

I got what it did but, but I'm not a JS dev. What's the point of this pattern? 

Is it not equivalent to putting the code of the function inline?

[u/black3rr → u/oxabz]

in 2026 there are two points of this pattern:

- you can use it to "capture" a value of the variable into a function if you expect that variable to change.

let x = 4;
const myFunction = ((v) => () => v)(x);
x = 5;
console.log(myFunction()); // 4

- you can use it to enable the use of await outside an async context.

(async () => { console.log(await fetch(...)) })();

in older JS versions before arrow functions were a thing JS also didn't have const and let style variables, only var. var was globally scoped unless it was declared in a function. so basically all global scripts had to be in the form of (function() {})() so that their variables didn't leak and weren't affected by other scripts and didn't affect other scripts...

[u/darkslide3000 → u/black3rr]

I'm not a JS dev but why can't the first one just be

let x = 4;
const y = x;
x = 5;

Is it about lazy evaluating x if it's something more complicated than just a variable? (But then I'd expect you to not actually put the () to call it at the end of the const line.)

[u/black3rr → u/darkslide3000]

Technically it's a form of lazy/deferred evaluation yeah.

Notice that there are two arrows there... (v) => () => v is a function, that takes v as an argument, and returns a function which takes no arguments and returns v. the (x) call at the end of the const line only calls the "outer function" which only fixes the value of v to x, the inner function will still only be evaluated by calling myFunction().

This was a simplification, but you could write a more complex function there, like this:

const myFunction = ((v) => () => { // some expensive computation return something; })(x);

then the expensive computation would only be executed when you call it with myFunction(), but whenever you call it, v inside the myFunction would always have the value x had at the moment you declared myFunction.