Example
// rectangle object: { x:, y:, width:, height: }
// circle object: { x:, y:, radius: }
// return true if the rectangle and circle are colliding
function RectCircleColliding(rect,circle){
var dx=Math.abs(circle.x-(rect.x+rect.width/2));
var dy=Math.abs(circle.y-(rect.y+rect.height/2));
if( dx > circle.radius+rect.width/2 ){ return(false); }
if( dy > circle.radius+rect.height/2 ){ return(false); }
if( dx <= rect.width ){ return(true); }
if( dy <= rect.height ){ return(true); }
var dx=dx-rect.width;
var dy=dy-rect.height
return(dx*dx+dy*dy<=circle.radius*circle.radius);
}
