Make a Layer Bounce Expression

//MAKE A LAYER BOUNCE:
bounceSpeed=7;
flight=01;
bounceHeight=3.5;
t=Math.abs((time*2*bounceSpeed)%2-1);
t=linear(t,flight,0,0,1);
b=Math.cos(t*Math.PI/2);
value - [0,bounceHeight*b];