Closest Location

This is a tiny and simple script created in response to this question, http://stackoverflow.com/questions/21279559/geolocation-closest-locationlat-long-from-my-position

All credit goes to Andrew for the original code, http://stackoverflow.com/users/622104/andrew-opengeocode

Installation

If you are using jQuery, then simply just add the file to your index.html and you are right to go.

If you are using Angular, then copy the code into a service and make sure to create the closestLocation function on the service's scope like so:

this.closestLocation = closestLocation;

How to use

There's only three things you need to bring to this pool party, a latitude, a longitude and an array of arrays that contains your locations that you want to compare the latitiude and longitiude too. The array of arrays must be structed like below:

var locations = [
  ['Name of Location', latitude, longitude],
  ['Name of Location', latitude, longitude],
  ['Name of Location', latitude, longitude]
]

When you've got all three things. Just pass each variable into the closestLocation function like so:

closestLocation(latitude, longitude, locations);

Obviously, if you are using Angular it would look something more similiar to this:

LocationService.closestLocation(latitude, longitude, locations);

The function will return the array that is closest to the latitude and longitude you passed it.

Say you wanted to get just the name of the location that is closest? Easy.

// Store the value returned from closestLocation into a variable
var close = closestLocation(latitude, longitude, locations);
// Then grab the value at the first index of the array
close[0]

Example

Most people will want to use this code to work out what city etc is closest to a users location.

This can achieved using the Geolocation API in browsers these days.

// get our three parameters ready
var lng,
    lat,
    cities = [
["Sydney",    -33.867487,  151.206990],
["Melbourne", -28.083627,  -80.608109],
["Brisbane",  -27.471011,  153.023449],
["Adelaide",  -34.928621,  138.599959],
["Perth",     -31.953513,  115.857047]
];

// HTML5/W3C Geolocation
if (navigator.geolocation) {
  // get the users current position
  navigator.geolocation.getCurrentPosition(function(position) {
    // store their latitude and longitude into the variables we set up above
    lng = position.coords.latitude;
    lat = position.coords.longitude;
    
    // in this case I just want the name of the city, so I'm storing the returned value into a variable
    var usersCity = closestLocation(lng, lat, cities);
    
    // I want to keep this value for when the user returns to the site or app
    window.localStorage.usersLocation = usersCity[0];

  }, function(error) {
    // logs the error if we can't get the users current position for some reason
    console.log(error);
  });
}