判断点击的点位是否在polygon之内(微信小程序）

// 判断点击的点位是否在polygon之内
			isPtInPoly(aLat, aLon, pointList) {
    
    
				/* 
				:param aLat: double 纬度 
				:param aLon: double 经度 
				: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 
				*/
				let iSum = 0  
				let iCount = pointList.length
						      
				if(iCount < 3) {
    
    
					return false 
				}
				for(let i = 0; i < iCount;i++) {
    
    
					let pLat1 = pointList[i].latitude  
					let pLon1 = pointList[i].longitude
					let pLat2 = 0, pLon2 = 0;
					if(i == iCount - 1) {
    
    
						pLat2 = pointList[0].latitude
						pLon2 = pointList[0].longitude
					} else {
    
    
						pLat2 = pointList[i + 1].latitude  
						pLon2 = pointList[i + 1].longitude
					}
					if (((aLat >= pLat1) && (aLat < pLat2)) || ((aLat>=pLat2) && (aLat < pLat1))) {
    
    
						if (Math.abs(pLat1 - pLat2) > 0) {
    
    
						    let pLon = pLon1 - ((pLon1 - pLon2) * (pLat1 - aLat)) / (pLat1 - pLat2);  
						    if(pLon < aLon) {
    
    
						        iSum += 1 
						    }
				   	    }
				    } 
			    }
				if(iSum % 2 != 0) {
    
    
					return true  
				}else {
    
    
					 return false 
				}  
			},