javascript - 查找距离我当前位置最近的 friend

Question

我想通过手机获取距离我当前位置较近的 friend 的位置来找到他们。例如，在下面的代码中，我有 var 城市，如果我输入 3,4 个 friend 的号码，我可以这样做吗？或者我可以做一些其他改变吗？可能吗？

// Get User's Coordinate from their Browser
window.onload = function () {
    // HTML5/W3C Geolocation
    if (navigator.geolocation) {
        navigator.geolocation.getCurrentPosition(UserLocation);
    }
    // Default to Washington, DC
    else
        NearestCity(38.8951, -77.0367);
}

// Callback function for asynchronous call to HTML5 geolocation
function UserLocation(position) {
    NearestCity(position.coords.latitude, position.coords.longitude);
}


// Convert Degress to Radians
function Deg2Rad(deg) {
    return deg * Math.PI / 180;
}

function PythagorasEquirectangular(lat1, lon1, lat2, lon2) {
    lat1 = Deg2Rad(lat1);
    lat2 = Deg2Rad(lat2);
    lon1 = Deg2Rad(lon1);
    lon2 = Deg2Rad(lon2);
    var R = 6371; // km
    var x = (lon2 - lon1) * Math.cos((lat1 + lat2) / 2);
    var y = (lat2 - lat1);
    var d = Math.sqrt(x * x + y * y) * R;
    return d;
}

var lat = 20; // user's latitude
var lon = 40; // user's longitude

var cities = [
      ["city1", 10, 50, "blah"],
        ["city2", 40, 60, "blah"],
        ["city3", 25, 10, "blah"],
          ["city4", 5, 80, "blah"]
];

function NearestCity(latitude, longitude) {
    var mindif = 99999;
    var closest;

    for (index = 0; index < cities.length; ++index) {
        var dif = PythagorasEquirectangular(latitude, longitude, cities[index]
        [1], cities[index][2]);
        if (dif < mindif) {
            closest = index;
            mindif = dif;
        }
    }

    // echo the nearest city
    alert(cities[closest]);
}

Answer 1

我建议使用GeoFire为此，它来自 firebase，并具有基于地理的查询，并且可以以简单的方式执行您想要的操作