小程序判断当前坐标点（位置）在不在覆盖物内

function IsPtInPoly(aLat, aLon, pointList) {
    /* 
    :param aLon: double 经度 
    :param aLat: double 纬度 
    :param pointList: list [{latitude: 22.22, longitude: 113.113}...] 多边形点的顺序需根据顺时针或逆时针，不能乱 
    */
    var iSum = 0  
    var iCount = pointList.length

    if(iCount < 3) {
        return false 
    }
    for(var i = 0; i < iCount;i++) {
        var pLat1 = pointList[i].latitude  
        var pLon1 = pointList[i].longitude
        if(i == iCount - 1) {
            var pLat2 = pointList[0].latitude
            var pLon2 = pointList[0].longitude
        } else {
            var pLat2 = pointList[i + 1].latitude  
            var pLon2 = pointList[i + 1].longitude
        }
        if (((aLat >= pLat1) && (aLat < pLat2)) || ((aLat>=pLat2) && (aLat < pLat1))) {
            if (Math.abs(pLat1 - pLat2) > 0) {
                var pLon = pLon1 - ((pLon1 - pLon2) * (pLat1 - aLat)) / (pLat1 - pLat2);  
                if(pLon < aLon) {
                    iSum += 1 
                }
            }
        } 
    }
    if(iSum % 2 != 0) {
        return true  
    }else {
        return false 
    }  
}
module.exports = {
    IsPtInPoly: IsPtInPoly,
};