已知两点，获得方位角

function GetAngle(x1, y1, x2, y2) {var angle = Math.atan((y1 - y2) /(x1 - x2)) * 180 / Math.PI ;if (x1 < x2 && y1 < y2) {//象限1angle = 90 - angle;} else if(x1 < x2 && y1 > y2) {//象限2angle = Math.abs(angle) + 90;} else if(x1 > x2 && y1 > y2) {//象限3angle = 270 - angle;} else if (x1 > x2 && y1 < y2) {//象限4angle = 270 + Math.abs(angle);}return Math.round(angle);};