Leap Motion Code to listing in my book TurnJs with it

gistfile1.txt

$(document).ready(function() {

    var ctl = new Leap.Controller({enableGestures: true});
    
    var swiper = ctl.gesture('swipe');
    
    var totalDistance = 0;
    
    var tolerance = 50;
    var cooloff = 300;
    
    var x = 2, y = 2;
    var turnLock = false;
    
    function turn( direction )
    {
        if ( turnLock )
            return;
    
        console.log( "flip to > " + direction );
        flipbook.turn( direction );
    
        // prevents flipping all through the book at once
        turnLock = true;
    
        setTimeout( function()
        {
            turnLock = false;
        }, 400 );
    }
    
    swiper.update(function(g) {
    
        if (Math.abs(g.translation()[0]) > tolerance || Math.abs(g.translation()[1]) > tolerance) {
    
            var xDir = Math.abs(g.translation()[0]) > tolerance ? (g.translation()[0] > 0 ? -1 : 1) : 0;
            var yDir = Math.abs(g.translation()[1]) > tolerance ? (g.translation()[1] < 0 ? -1 : 1) : 0;
    
            if (xDir===1 && yDir===0) { turn('previous'); }
            else if (xDir===-1 && yDir===0) { turn('next'); }
    
        }
    
    });
    
    ctl.connect();

});

Hello, i got some problem in this code ....
Uncaught ReferenceError: flipbook is not defined