How to return values from UseEffect Hook

Question

I am getting the latitude and longitude from a Use Effect hook (which I am relatively new to). I want to return the values outside the use effect hook and store them in variables or even state if needed. I can console log the values but do i just add a return statement or pass arguments somehow? What feature do i need to make use of? I plan to pass the lat and long data into other parts of code which is why i am trying to retrieve it from the useEffect hook.

useEffect(() => {
    if ("geolocation" in navigator) {
      console.log("Available");
    } else {
      console.log("Not Available");
    }
    navigator.geolocation.getCurrentPosition(function (position) {
      let lat = position.coords.latitude;
      let long = position.coords.longitude;
      console.log(lat);
      console.log(long);
    });
  }, []);

let newLat = lat?
let newLong = long?

Answer 1

You can save them in a state or a reference hook.

Here is how I would do it with a reference hook:

const lat = useRef(null);
const long = useRef(null);

useEffect(() => {
    if ("geolocation" in navigator) {
      console.log("Available");
    } else {
      console.log("Not Available");
    }
    navigator.geolocation.getCurrentPosition(function (position) {
      lat.current = position.coords.latitude;
      long.current = position.coords.longitude;
      console.log(lat);
      console.log(long);
    });
  }, []);

You can then access the lat and long values using .current on them. Changing them will not trigger a re-render.

If you want to use states you can do it like this

const [lat, setLat] = useState(null);
const [long, setLong] = useState(null);

useEffect(() => {
    if ("geolocation" in navigator) {
      console.log("Available");
    } else {
      console.log("Not Available");
    }
    navigator.geolocation.getCurrentPosition(function (position) {
      setLat(position.coords.latitude);
      setLong(position.coords.longitude);
      console.log(lat);
      console.log(long);
    });
  }, [setLat, setLong]);

And you can use them like any normal state.

Also make sure that their values are not null when trying to use them.