function fadeInP(element, duration = 300) {
	element.style.display = "block";
	var opacity           = 0;
	var intervalId        = setInterval(
		function () {
			if (opacity < 1) {
				opacity              += 0.1;
				element.style.opacity = Math.min( opacity, 1 );
			} else {
				clearInterval( intervalId );
			}
		},
		duration / 10
	);
}

function fadeOutP(element, duration = 300) {
	var opacity    = 1;
	var intervalId = setInterval(
		function () {
			if (opacity > 0) {
				opacity              -= 0.1;
				element.style.opacity = Math.max( opacity, 0 );
			} else {
				clearInterval( intervalId );
				element.style.display = "none";
			}
		},
		duration / 10
	);
}
