I am trying to calculate distance between two lats and longs in KM and show that distance in label or paragraph. I have an address from which I need to figure out lat1 and lon1. I am able to figure this out. I need to find lat2 and lon2 of my current location. I am able to figure this out

calculate distance between two coordinates in javascript?

I am trying to calculate distance between two lats and longs in KM and show that distance in label or paragraph.

I have an address from which I need to figure out lat1 and lon1. I am able to figure this out.
I need to find lat2 and lon2 of my current location. I am able to figure this out as well.

Now once I have lat1, lon1, lat2 and lon2 – I need to find distance between these coordinates. Below is my code but it is giving distance as NaN once I alert it. I am not sure what’s wrong here. Also is this the right way I am doing here?

<!DOCTYPE html>
<html>
<style>
body {
  margin: 0;
  padding: 0;
  font: 12px sans-serif;
}
h1, p {
  margin: 0;
  padding: 0;
}
#map_div{
    width:400px;
    height:400px;
    margin: 0 auto;
}
#outer {
    width:400px;
    height:50px;
    margin:0 auto;
    text-align:center;
}
#outer input[type="text"] {
    display: block;
    margin: 0 auto;
}

</style>
<body>
<script type="text/javascript" src="http://maps.googleapis.com/maps/api/js?v=3&amp;sensor=false"></script>

<div id="outer">
<p id="distance_text">this is 201 km away from</p>
<input type="text" name="location" value="Current Location"><br>
<div id="map_div"></div>
</div>

</body>
<script type="text/javascript">
var lat1;
var lon1;
var lat2;
var lon2;
var geocoder = new google.maps.Geocoder();
var address = "1750 riverside drive, ottawa, ontario, canada";

geocoder.geocode( { 'address': address}, function(results, status) {
if (status == google.maps.GeocoderStatus.OK) {
    lat1 = results[0].geometry.location.lat();
    lon1 = results[0].geometry.location.lng();
    }
});

var x = document.getElementById("distance_text");
getLocation();
function getLocation() {
    if (navigator.geolocation) {
        navigator.geolocation.watchPosition(showPosition);
    } else { 
        x.innerHTML = "Geolocation is not supported by this browser.";
    }
}

function showPosition(position) {
    lat2 = position.coords.latitude;
    lon2 = position.coords.longitude;
}
var distance = getDistanceFromLatLonInKm(lat1,lon1,lat2,lon2);
alert(distance);
function getDistanceFromLatLonInKm(lat1,lon1,lat2,lon2) {
  var R = 6371; // Radius of the earth in km
  var dLat = deg2rad(lat2-lat1);
  var dLon = deg2rad(lon2-lon1); 
  var a = 
    Math.sin(dLat/2) * Math.sin(dLat/2) +
    Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * 
    Math.sin(dLon/2) * Math.sin(dLon/2); 
  var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); 
  var d = R * c; // Distance in km
  return d;
}

function deg2rad(deg) {
  return deg * (Math.PI/180)
}
</script>
</html>

I need to replace 201 km with actual distance after calculating it. Here is my jsfiddle

Answer

You can use google maps distance method but it require LatLng objects

Try this:

const from = new google.maps.LatLng(lat1, lng1);
const to = new google.maps.LatLng(lat2, lng2);
const distance =  google.maps.geometry.spherical.computeDistanceBetween(from,to)

This is the working JSfiddle You may have to add API key in map script tag: https://jsfiddle.net/ruokyanv/

change p tag distance: yes you can inject js file in your html and use jquery $:

var distance = `this is ${distance} km away from`
$('#distance_text').val(distance)

Let me know if the issue still persists.

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Answer