判断一个元素是否出现

<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8"/>
	<title></title>
	<style type="text/css">
		html, body {
			width: 3000px;
		}
		#ys {
			background-color: #ff0000;
		}
	</style>
</head>
<body>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<div id="ys">nihao</div>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<p>adsas</p>
<script type="text/javascript" src="js/jquery-1.10.2.js"></script>
<script type="text/javascript">
	$(window).scroll(function () {
		if ($("#ys").is(check)) {
			console.log("出现了");
		}

		function check() {
			var $this = $(this);
			var $thisOffsetTop = $this.offset().top;
			var $thisOffsetLeft = $this.offset().left;

			if ($thisOffsetTop <= $(window).scrollTop() + $(window).height() &&
					$thisOffsetTop + $this.height() >= $(window).scrollTop() &&
					$thisOffsetLeft <= $(window).scrollLeft() + $(window).width() &&
					$thisOffsetLeft + $this.width() >= $(window).scrollLeft()) {
				return true;
			}
			return false;
		}
	});
</script>
</body>
</html>

  

posted @ 2014-11-21 14:36  zhishaofei3  阅读(196)  评论(0编辑  收藏  举报