Math.getShortestAngle will return the shortest angle between the two given angles. Angles are in the range -180 to 180, which is what Sprite.angle uses. So you can happily feed this method two sprite angles, and get the shortest angle back between them (phaserjs#2494)

photonstorm · photonstorm · commit 688752c5dee4 · 2016-07-29T03:39:51.000+01:00
diff --git a/README.md b/README.md
@@ -315,6 +315,7 @@ You can read all about the philosophy behind Lazer [here](http://phaser.io/news/
 * Group.iterate has a new `returnType`: `RETURN_ALL`. This allows you to return all children that pass the iteration test in an array.
 * The property `checkCollision.none` in the ArcadePhysics.Body class was available, but never used internally. It is now used and checked by the `separate` method. By setting `checkCollision.none = true` you can disable all collision and overlap checks on a Body, but still retain its motion updates (thanks @samme #2661)
 * Math.rotateToAngle takes two angles (in radians), and an interpolation value, and returns a new angle, based on the shortest rotational distance between the two.
+* Math.getShortestAngle will return the shortest angle between the two given angles. Angles are in the range -180 to 180, which is what `Sprite.angle` uses. So you can happily feed this method two sprite angles, and get the shortest angle back between them (#2494)
 
 ### Updates
 
diff --git a/src/math/Math.js b/src/math/Math.js
@@ -371,6 +371,30 @@ Phaser.Math = {
 
     },
 
+    /**
+    * Gets the shortest angle between `angle1` and `angle2`.
+    * Both angles must be in the range -180 to 180, which is the same clamped
+    * range that `sprite.angle` uses, so you can pass in two sprite angles to
+    * this method, and get the shortest angle back between the two of them.
+    *
+    * The angle returned will be in the same range. If the returned angle is
+    * less than 0 then it's a counter-clockwise rotation, if >= 0 then it's
+    * a clockwise rotation.
+    * 
+    * @method Phaser.Math#getShortestAngle
+    * @param {number} angle1 - The first angle. In the range -180 to 180.
+    * @param {number} angle2 - The second angle. In the range -180 to 180.
+    * @return {number} The shortest angle, in degrees. If less than zero it's counter-clockwise, otherwise clockwise.
+    */
+    getShortestAngle: function (angle1, angle2) {
+
+        var difference = angle2 - angle1;
+        var times = Math.floor((difference - (-180)) / 360);
+
+        return (difference - (times * 360)) * -1;
+
+    },
+
     /**
     * Find the angle of a segment from (x1, y1) -> (x2, y2).
     * 
