Is there any other way to implement a “listening” function without an infinite while loop?

Question

I\'ve been thinking a lot about code and libraries like React that automatically, well, react to events as they happen, and was wondering about how all of that is implemente

Answer 1

"listeners" and "subscriptions" are just ideas. Everything can be abstracted with lambdas. Here is one possible implementation -

const logger =
  // create a new "listener",
  // send any data we "hear" to console.log
  listen(console.log)

// implement so-called "listener"
const listen = (responder) =>
  x => (responder(x), x)

// run it synchronously
logger(1)
logger(2)

// or asynchronously
setTimeout(_ => logger(3), 2000)

// 1
// 2
// some time later...
// 3

So let's say we have a