js-Touch screen slide to determine the sliding direction (mobile version)

var startx, Starty;
Get angle
function Getangle (ANGX, angy) {
Return math.atan2 (Angy, ANGX) * 180/MATH.PI;
};

Return direction 1 up 2 down 3 Left 4 right 0 not sliding according to the starting point
function Getdirection (startx, Starty, EndX, Endy) {
var angx = Endx-startx;
var angy = Endy-starty;
var result = 0;

If the sliding distance is too short
if (Math.Abs (ANGX) < 2 && Math.Abs (Angy) < 2) {
return result;
}

var angle = Getangle (ANGX, angy);
if (angle >= -135 && angle <=-45) {
result = 1;
} else if (Angle > $ && Angle < 135) {
result = 2;
} else if ((angle >= 135 && Angle <= 180) | | (Angle >= -180 && Angle <-135)) {
result = 3;
} else if (angle >= -45 && Angle <= 45) {
result = 4;
}

return result;
}
Finger touch Screen
Document.addeventlistener ("Touchstart", function (e) {
StartX = E.touches[0].pagex;
Starty = E.touches[0].pagey;
}, False);
Finger off the screen
Document.addeventlistener ("Touchend", function (e) {
var endx, Endy;
EndX = E.changedtouches[0].pagex;
Endy = E.changedtouches[0].pagey;
var direction = Getdirection (StartX, Starty, EndX, Endy);
switch (direction) {
Case 0:
Alert ("Not sliding! ");
Break
Case 1:
Alert ("Up! ")
Break
Case 2:
Alert ("Down! ")
Break
Case 3:
Alert ("Left! ")
Break
Case 4:
Alert ("Right! ")
Break
Default
}
}, False);

js-Touch screen slide to determine the sliding direction (mobile version)