下面是一个根据经纬度计算两点间距离的方法记录：
function rad(d){
return d * Math.PI / 180.0;
}
module.exports = function getDistance(addr1,addr2,autoFormat = false){
const EARTH_RADIUS = 6378137;
const lon1 = addr1.lon;
const lat1 = addr1.lat;
const lon2 = addr2.lon;
const lat2 = addr2.lat;
let radLon1 = rad(lon1)
let radLon2 = rad(lon2)
let radLat1 = rad(lat1)
let radLat2 = rad(lat2)
if(radLat1 < 0){
radLat1 = Math.PI / 2 + Math.abs(radLat1);// south
}
if(radLat1 > 0){
radLat1 = Math.PI / 2 - Math.abs(radLat1);// north
}
if(radLon1 < 0){
radLon1 = Math.PI * 2 - Math.abs(radLon1);// west
}
if(radLat2 < 0){
radLat2 = Math.PI / 2 + Math.abs(radLat2);// south
}
if(radLat2 > 0){
radLat2 = Math.PI / 2 - Math.abs(radLat2);// north
}
if(radLon2 < 0){
radLon2 = Math.PI * 2 - Math.abs(radLon2);// west
}
const x1 = EARTH_RADIUS * Math.cos(radLon1) * Math.sin(radLat1);
const y1 = EARTH_RADIUS * Math.sin(radLon1) * Math.sin(radLat1);
const z1 = EARTH_RADIUS * Math.cos(radLat1);
const x2 = EARTH_RADIUS * Math.cos(radLon2) * Math.sin(radLat2);
const y2 = EARTH_RADIUS * Math.sin(radLon2) * Math.sin(radLat2);
const z2 = EARTH_RADIUS * Math.cos(radLat2);
const d = Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2) + (z1 - z2) * (z1 - z2));
//余弦定理求夹角
const theta = Math.acos((EARTH_RADIUS * EARTH_RADIUS + EARTH_RADIUS * EARTH_RADIUS - d * d) / (2 * EARTH_RADIUS * EARTH_RADIUS));
const dist = (theta * EARTH_RADIUS);
if(autoFormat){
if(dist < 1000){
return dist + "m"
}else{
return dist / 1000 + "km"
}
}
return dist;
}
其中，getDistance 接收两个位置信息作为参数，以及一个是否自动格式化的可选参数，当此参数传为 true 时，会对返回值进行转换。
完。
