js漸變，直到消失

	var oI = setInterval(function() {
			var t1 = new Date('2019-06-05 20:01:00').getTime();
			var t2 = new Date().getTime();
			var t = t1 - t2;
			var tm = '';
			if (t < 1000 * 60 * 60 * 24) {
				tm = 1000 * 60 * 60 * 24;
			}
			var o = (t / tm).toFixed(2);
			if (t > 0.05) {
				document.getElementsByTagName("body")[0].style.opacity = o;
			} else {
				document.getElementsByTagName("body")[0].style.opacity = 0.05;
				clearInterval(oI);
			}       
		}, 1000);