JavaScript: Find the angle between two points

angle-between-points.js

var angleBetweenPoints = function(p1, p2, rad){ // vector2, vector2, bool
  if (!p1 || !p2){
      return false;
  }
  // format angle in radians
  var angleRadians = Math.atan2(p2.y - p1.y, p2.x - p1.x);
  // format angle in degrees
  var angleDegrees = angleRadians * 180 / Math.PI;

  // return formatted angle
  if (rad) return angleRadians;
  return angleDegrees;
}