What are some real life applications of generators in Javascript?

Question

Generators

Answer 1

Generators are like lists but you don't have to generate the whole list at once which potentially saves time.

function* foo () {
for (let i = 0; i < 100; i++)
yield long_computation(i);
}

Now, `[...foo()]` gives a list of length 100 with all the results but you can also stop earlier:

for (let value of foo())
if (value < 0)
break;

This is better than generating the whole list which takes a long time and then throwing away the last 90 elements!

Some things we can do with generators:

- Infinite generators, like a generator that generates all possible prime numbers, one after the other.

- Take input multiple times:

function* chatBot() {
const age = yield "Please enter your age: ";
const name = yield "And your name: ";
return "Thanks!";
}

let bot = chatBot();
let input, msg;

while (true) {
let { value, done } = bot.next(input);
msg = value;
if (done) break;
input = prompt(msg);
}

alert(msg);

And many other things but I'm running out of space.

Answer 2

Schindlabua yeah thanks. I understand generators but I don't know how useful they are. For example when I learned promises, I applied it in nodejs when I was working with APIs but for generators, apart from infinitely producing some values one at a time, I don't know other applications of it.

Answer 3

Schindlabua Thanks very much 😊 ❤️

Answer 4

Andrei I es6 generators

Answer 5

Edward We can draw parallels here. If promises are a replacement for nodejs-style callbacks, then generators can serve as a replacement for finite-state machines.

And those are everywhere. Say in a function that models a game of chess you would need to pass in whose turn it is, as an argument, but a generator can just remember it.

I think generators are a bit under-utilized and not so mainstream (yet!) and so they don't come up in my day-to-day programming a lot either. But you can find many cool applications for them if you keep an eye out.

(Performance is pretty bad if you yield a lot so that sucks)

Also nice: async generators are a thing now so we have even more ways to deal with Promises and such.

Another tool in the toolbox am I right :)

Answer 6

Generators of what?

Answer 7

Mirielle That sounds plausible. Thanks a lot. 😊😊