Javascript - 从嵌套函数返回一个值

Question

I'm trying to ReverseGeocode an address from it's lat and long values and display in on a Bootstrap modal, and so I would like to update the variable ' startAddress ' with the result from the ReverseGeocode function but I've been unable to.

This is the modal function:

$(document).on("click", ".modal-editRoute", function () {
    var getCoord = $(this).attr("data");
    var splitCoord = getCoord.split(",");
    var startAddress = getReverseGeocodingData(splitCoord[0], splitCoord[1]);
    console.log("1: "+ startAddress); // This is undefined
    $(".modal-body #startRoute").val(startAddress);
    $(".modal-body #endRoute").val('coming soon');
});

This is the getReverseGeocodingData function:

function getReverseGeocodingData(lat, lng) {
    var latlng = new google.maps.LatLng(lat, lng);
    var geocoder = new google.maps.Geocoder();
    geocoder.geocode({ 'latLng': latlng }, function (results, status) {
        if (status !== google.maps.GeocoderStatus.OK) {
            alert(status);
        }
        if (status == google.maps.GeocoderStatus.OK) {
            var result = (results[0].formatted_address);
        }
        console.log("2: "+result);
        return result;
    });
}

This is how it shows up in the console logs :

Answer 1

You can use promises:

function getReverseGeocodingData(lat, lng) {
    var latlng = new google.maps.LatLng(lat, lng);
    var geocoder = new google.maps.Geocoder();
    return new Promise((resolve, reject) => {
        geocoder.geocode({ 'latLng': latlng }, function (results, status) {
            if (status !== google.maps.GeocoderStatus.OK) {
                alert(status);
            }
            if (status == google.maps.GeocoderStatus.OK) {
                var result = (results[0].formatted_address);
                startAddress = result;
            }
            console.log("2: "+startAddress); // This has the proper value
            resolve(startAddress);
        });
    });
}

$(document).on("click", ".modal-editRoute", function () {
    var getCoord = $(this).attr("data");
    var splitCoord = getCoord.split(",");
    getReverseGeocodingData(splitCoord[0], splitCoord[1])
      .then((startAddress) => {
          console.log("1: "+ startAddress); // This is empty
          $(".modal-body #startRoute").val(startAddress);
          $(".modal-body #endRoute").val('coming soon');
      });
});

To learn more about promises you can read this post: Promise