How to write a javascript function that figures out the angle of two points? -

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assuming straight line pointing north 0 degrees , goes 359. if given 2 points each x , y value, how find out "angle" makes between first point , second point? assuming (arctan2) function exists okay.

i have following:

    var x = x2 - x1;     var y = y2 - y1;     var radian = arctan2(y, x);     var degrees = radian * 180 / 3.14;

i seem getting "0 degrees" on right arrow , 270 pointing north instead of 0 degrees looking towards north.

if coordinate system have 0 degrees pointing up/north x comes first atan2 function:

var x = x2 - x1; var y = y2 - y1; var angledegrees = math.atan2(x, y) * 180 / math.pi;  if (angledegrees < 0) angledegrees += 360;  // force positive value

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