Get latitude and longitude from browser

geocoding.js

// if the browser supports the w3c geo api
if(navigator.geolocation){
  // get the current position
  navigator.geolocation.getCurrentPosition(

  // if this was successful, get the latitude and longitude
  function(position){
    var lat = position.coords.latitude;
    var lon = position.coords.longitude;
  },
  // if there was an error
  function(error){
    alert('ouch');
  });
}