Calculating Distance

CalculateDistance.js

export default (request) => { 
  const kvstore = require('kvstore'); 
  const xhr = require('xhr'); 
  const pubnub = require('pubnub'); 
  const message = JSON.parse(request.message); 
  console.log(message); 
  kvstore.getItem(message[1]).then((value) => { 
    var location = JSON.parse(value); 
    var distanceDelta = distance(message[2], message[3], location.lat, location.long, "K"); 
    pubnub.publish({ 
      "message":{ "ID": message[1], "distance": distanceDelta }, 
      "channel": `${message[0]}-distance` 
    }).then(); }) 
  return request.ok(); 
  // Return a promise when you're done 
} 
function distance(lat1, lon1, lat2, lon2, unit) { 
  if ((lat1 == lat2) && (lon1 == lon2)) { 
    return 0; 
  } else { 
    console.log(lat1, lon1, lat2, lon2); 
    var radlat1 = Math.PI * lat1/180; 
    var radlat2 = Math.PI * lat2/180; 
    var theta = lon1-lon2; 
    var radtheta = Math.PI * theta/180; 
    var dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
    if (dist > 1) { 
      dist = 1; 
    } 
    dist = Math.acos(dist); 
    dist = dist * 180/Math.PI; 
    dist = dist * 60 * 1.1515; 
    if (unit=="K") { 
      dist = dist * 1.609344 
    } 
    if (unit=="N") { 
      dist = dist * 0.8684 
    } 
    return dist; 
  } 
}