Using variables from function in another function

Question

I am using the selectedIndex of a form to assign values to variables

function getIndex() {
var departureAirportIndex = document.getElementById("mySelect").selectedIndex;        

if (departureAirportIndex == 1) {
var lat2 = 13.7563309;
var lon2 = 100.5017651;
}
if (departureAirportIndex == 2){
  var lat2 = 41.977226;
  var lon2 = -87.836723;
}
if (departureAirportIndex == 3){
  var lat2 = -37.663712;
  var lon2 = 144.844788;
}

After assigning the values I would like to use the values in a function which calculates the distance.

function getDistance(lat1, lon1, lat2, lon2, unit) {
  var lat1 = 40.730610;
  var lon1 = -73.935242;
  var unit = "K";
                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);
                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.toFixed(2)

}

How can I use the lat2 and lon2 variables in the second function? After trying several options and reading about scoping I can't get it to work.

You have to declare them outside the first function, as globals or to pass them as parameters of the second function. — Striped
– Striped, Commented Mar 6, 2018 at 20:08
Thought about this, but almost everybody is telling me not to declare variables in the global scope — stevv
– stevv, Commented Mar 7, 2018 at 19:50

Ele · Accepted Answer · 2018-03-06 20:12:01Z

3

You can return an object with the coordinates:

function getIndex() {
    var coordinates = {}
    var departureAirportIndex = document.getElementById("mySelect").selectedIndex;        

    if (departureAirportIndex == 1) {
        coordinates.lat = 13.7563309;
        coordinates.lon = 100.5017651;
    }
    if (departureAirportIndex == 2){
        coordinates.lat = 41.977226;
        coordinates.lon = -87.836723;
    }
    if (departureAirportIndex == 3){
        coordinates.lat = -37.663712;
        coordinates.lon = 144.844788;
    }

    return coordinates;
}

function getDistance(lat1, lon1, lat2, lon2, unit) {...}

var coordinates = getIndex();
getDistance(lat1, lon1, coordinates.lat, coordinates.lon, unit);

answered Mar 6, 2018 at 20:12

Ele

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