Calculate bearing between 2 points with javascript

Question

I want to calculate the bearing from point 1 to point 2 The input format is 52.070564 - 4.407116

No matter what i try i cannot get an correct output.

The for

Answer 1

start_latitude  = 12.9389352
start_longitude = 77.6994306
stop_latitude   = 12.939103
stop_longitude  = 77.705825

var y = Math.sin(stop_longitude-start_longitude) * Math.cos(stop_latitude);
var x = Math.cos(start_latitude)*Math.sin(stop_latitude) -
        Math.sin(start_latitude)*Math.cos(stop_latitude)*Math.cos(stop_longitude-start_longitude);
var brng = Math.atan2(y, x) * 180 / Math.PI;


alert("Bearing in degreee:  " + brng);