javascript - 在另一个函数中使用函数中的变量

Question

我正在使用表单的 selectedIndex 为变量赋值

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;
}

分配值后，我想在计算距离的函数中使用这些值。

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)

}

如何在第二个函数中使用 lat2 和 lon2 变量？在尝试了几种选项并阅读了有关范围界定的内容后，我无法让它发挥作用。

Answer 1

您可以返回一个带有坐标的对象:

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);