const easing = { linear ( x , _t , b , c ) { return b + ( c - b ) * x ; } , swing ( x , t , b , c , d ) { return easing . easeInOutQuad ( x , t , b , c , d ) ; } , easeInOutQuad ( _x , t , b , c , d ) { if ( ( t /= d / 2 ) < 1 ) return ( c / 2 ) * t * t + b ; return ( - c / 2 ) * ( -- t * ( t - 2 ) - 1 ) + b ; } , } ; export default easing ;