Set object values from asynchronous function

The most important question is: when are you trying to access PositionObj's properties? Since the whole thing is asynchronous, you won't see any value in lat or lon until the location is retrieved and getPos assigns it. Thus, something synchronous like:

getInfo();
console.log(PositionObj.lat);

is definitely not going to work. getInfo returns immediately and doesn't wait for the location to come in. That's a good thing: the whole idea about asynchronism is that you don't wait (block) until you get your results. Instead, you give a callback to the function and that function makes sure to call it when the results are retrieved later on. In Hollywood style: "don't call me, I call you!"

Thus, anything that relies on the actual position retrieved by getInfo needs to be in the callback. This means that you have to think and code differently: you'll need to break up your synchronous function into smaller functions which are chained up as callbacks.

In your case, you'd put that console.log(PositionObj.lat) (or anything else you want to do with the position) inside (what you called) getPos (you probably want to think of a better name for that function though).

Here's a more complete example which demonstrates the concept better. An online shop may have something like this on its checkout page:

var position = getPosition(); // using geolocation
var closestShop = getClosestShop(position); // using AJAX to a server-side script
alert("The closest shop is " + closestShop);

However, all those synchronous calls would block the script's execution and the page would "freeze". The user would probably think that his browser crashed, and that's not a great user experience.

If all these actions were asynchronous, you'd restructure it so it looks like this:

getPosition(function(position) {
    getClosestShop(position, function(closestShop) {
        alert("The closest shop is " + closestShop);
    });
});

Here, each function accepts a callback function which it calls when the results are in. They all return immediately, allowing the script to continue execution and keep the page responsive. Of course, nothing stops you from starting another asynchronous action from within this callback, effectively chaining them up.

In fact, this last pattern is so popular that a new mechanism was created to make it more manageable: promises. The inner workings are still the same (functions accepting a callback instead of blocking synchronously) but it looks more pleasant. When you make getPosition and getClosestShop return a promise, you could write:

getPosition().then(getClosestShop).then(function(closestShop) {
    alert("The closest shop is " + closestShop);
});