使用函数内的变量设置新变量

Question

I am creating a web app using geolocation. So far I have it set up and working so when the user visits they are prompted to allow location services, then are presented with an alert (Not permanent, just for testing purposes.)

I am using this:

navigator.geolocation.getCurrentPosition(foundLocation, noLocation, {enableHighAccuracy:true});

function foundLocation(position)
{
    var lat = position.coords.latitude;
    var long = position.coords.longitude;
    alert('We know you are here '+ lat +','+ long);
}
function noLocation()
{
    alert('Could not find location');
}

Then I have a variable outside this called "address" which is the URL for the API call:

address = "http://api.wunderground.com/api/geolookup/hourly/conditions/astronomy/alerts/forecast/q/[LOCATION].json"

My question is how can I get the lat and long out of the function and insert them into the URL? I have tried a few methods, but they all return "undefined" so I am obviously doing something wrong.

Any help is greatly appreciated!

Thank you.

Answer 1

You have to understand the scope of a javascript variable, please, read this post: What is the scope of variables in JavaScript?

var address = '';

function setLocation(position)
{
    var lat = position.coords.latitude;
    var long = position.coords.longitude;
    address = "http://api.wunderground.com/api/geolookup/hourly/conditions/astronomy/alerts/forecast/q/" + lat + "," + long + ".json";
}

Besides, there is a better approach to solve your problem. The easiest approach is to create a global object with a unique name, with your variables as properties of that object and methods to change the variables, like:

var geolocation = {};
geolocation.latitude = 0;
geolocation.longitude = 0;
geolocation.address = "";
geolocation.setLocation = function(position) {
    geolocation.latitude = position.coords.latitude;
    geolocation.longitude = position.coords.longitude;
    geolocation.address = "http://api.wunderground.com/api/geolookup/hourly/conditions/astronomy/alerts/forecast/q/" + geolocation.latitude + "," + geolocation.longitude + ".json";
};
geolocation.show = function() {
  alert(geolocation.latitude + " " geolocation.longitude + " " + geolocation.address);
};

And so on. Now, everywhere in your file if you use:

geolocation.setLocation(position);
geolocation.show();

It will show the new values from the global object.

UPDATE

Keep in mind that a variable or object in javascript will be global if there is no wrapper around it, like another function or object.

Answer 2

Can you not just update the address directly from the function like this?

navigator.geolocation.getCurrentPosition(foundLocation, noLocation, {enableHighAccuracy:true});
var address = "http://api.wunderground.com/api/geolookup/hourly/conditions/astronomy/alerts/forecast/q/[LOCATION].json"

function foundLocation(position)
{
    var lat = position.coords.latitude;
    var long = position.coords.longitude;
    alert('We know you are here '+ lat +','+ long);
    address = address.replace('[LOCATION]', lat + ',' + long);
}