easing easeOutIn effect

easing.js

	/******************************************************************************/
	/*********************************** EASING ***********************************/
	/******************************************************************************/

(function() {
	// based on easing equations from Robert Penner (http://www.robertpenner.com/easing)

	var baseEasings = {};

	$.each( [ "Quad", "Cubic", "Quart", "Quint", "Expo" ], function( i, name ) {
		baseEasings[ name ] = function( p ) {
			return Math.pow( p, i + 2 );
		};
	});

	$.extend( baseEasings, {
		Sine: function( p ) {
			return 1 - Math.cos( p * Math.PI / 2 );
		},
		Circ: function( p ) {
			return 1 - Math.sqrt( 1 - p * p );
		},
		Elastic: function( p ) {
			return p === 0 || p === 1 ? p :
				-Math.pow( 2, 8 * (p - 1) ) * Math.sin( ( (p - 1) * 80 - 7.5 ) * Math.PI / 15 );
		},
		Back: function( p ) {
			return p * p * ( 3 * p - 2 );
		},
		Bounce: function( p ) {
			var pow2,
				bounce = 4;

			while ( p < ( ( pow2 = Math.pow( 2, --bounce ) ) - 1 ) / 11 ) {}
			return 1 / Math.pow( 4, 3 - bounce ) - 7.5625 * Math.pow( ( pow2 * 3 - 2 ) / 22 - p, 2 );
		}
	});


	$.each( baseEasings, function( name, easeIn ) {
		$.easing[ "easeIn" + name ] = easeIn;
		$.easing[ "easeOut" + name ] = function( p ) {
			return 1 - easeIn( 1 - p );
		};
		$.easing[ "easeInOut" + name ] = function( p ) {
			return p < 0.5 ?
				easeIn( p * 2 ) / 2 :
				1 - easeIn( 2  - 2 *p) / 2;
		};

		$.easing[ "easeOutIn" + name ] = function( p ) {
			return p < 0.5 ?
				0.5 * (1 - easeIn( 1 - 2 *p )):
				0.5 * easeIn(p * 2 - 1) + 0.5;
		};


	});
})();	

DEMO see http://blog.w3cub.com/easing/