for循环中的距离计算不起作用

Question

Im now currently developing test geolocation app.

I found some codes which are helpful for distance between two points (with latitude longitude coords.) and now im trying is, do loop that formula in for loop to get distance not only two points but many.

lets say I got one reference point, point X, and many other points, and Id like to get each distance between X and A, X and B and so on.

each longitude and latitude of the other points are set in associative-dimensional array like this,

    var response = (

    {

    id = 2;

    latitude = "50";

    longitude = "0";

    username = AAA;

    },

    {

    id = 5;

    latitude = "51";

    longitude = "-1";

    username = BBB;

    },

    {

    id = 6;

    latitude = "52";

    longitude = "-3";

    username = CCC;

    }

    )


    //and pointX data is
    var lat1 = "50";
    var lon1 = "0";

what im trying is;

    for(var i = 0; i < response.length; i++){

        var lat2 = response[i].latitude;
        var lon2 = response[i].longitude;

    //distance in kilometer
    function distance(lat1, lon1, lat2, lon2,response) {
        var radlat1 = Math.PI * lat1/180;
        var radlat2 = Math.PI * lat2/180;
        var radlon1 = Math.PI * lon1/180;
        var radlon2 = Math.PI * lon2/180;
        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);
        dist = Math.acos(dist);
        dist = dist * 180/Math.PI;
        dist = dist * 60 * 1.1515;
        dist = dist * 1.609344;
        return response[i].distanceKm = dist;
    }

but when i run this and output, for example, response[1].distanceKm is Undefined. smthng seems to go wrong. but i have no idea... any suggestion?

thank you in advance.

Answer 1

Your response code declaration is not declared as an array. It used ( and ) , not [ and ] like an array would use. Thus, there is no response[1] (eg it's undefined).

Arrays are declared using [ and ] like this:

var response = [ /* comma separate data elements here */ ];

Answer 2

As jfriend00 said, response[1] is undefined. Also you've incorrect object literal definition:

{  id = 5;
   latitude = "51";
   longitude = "-1";
   username = BBB;
 },

should be:

{  id : 5,
   latitude : "51",
   longitude : "-1",
   username : BBB
 },

etc.