移动开发过程中经常要用埋点来促进产品的改进,在native端做埋点相对来说简单一点,比如曝光,在view的类中可以使用显示回调来做,但在网页中要如何做埋点呢,比如要知道一个div标签的曝光次数应该怎么做,类比客户端自然是想知道有没有类似显示的回调,很不幸,Html里没有这个事件回调,但onload是有的,要实现曝光埋点,需要自己实现曝光事件的检测.以下是实现思路:
曝光,即是标签从浏览器中不可见到可见区域内时触发,关键就是要检测标签当前的位置还有当前可见区域的位置.如果这标签的所表示的区域矩形和可见区域相交,则可以认为标签被看到.那么就要分别计算标签区域大小和坐标和可见区域大小和坐标.
可见区域坐标和大小可以使用window对象获取scrollTop,scrollLeft和clientWidth,clientHeight来得到.标签的大小可以通过getElementById来获取到div对象然后得到相应属性.为了效率,我们可以先在body加载完后先获得好标签的大小和位置,然后在窗口的滚动时实时计算可见区域,并且计算可见区域是否和各个标签区域相交由此得到标签是否可见,以下是代码:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script type="text/javascript">
window.onscroll = function() {
var scrollTop = document.body.scrollTop || document.documentElement.scrollTop;
var scrollBottom = scrollTop + window.innerHeight;
var found = "";
for (var i = 0; i < positions.length; i++) {
var item = positions[i];
if ( scrollTop < (item[1] + item[3]) && scrollBottom > item[1]) {
console.log((i + 1) + " in screen")
found += ((i + 1) + ",")
}
}
document.getElementById("info").innerHTML = found + "in screen";
}
</script>
<style type="text/css">
.span {
text-align: center;
font-size: 50pt;
}
</style>
</head>
<body id="body">
<div id="0" style="width: 200px; height: 500px; background-color: #FF00FF"><div align="center"><span class="span">1</span></div></div>
<div id="1" style="width: 200px; height: 500px; background-color: #00FFFF"><div align="center"><span class="span">2</span></div></div>
<div id="2" style="width: 200px; height: 500px; background-color: #FFFF00"><div align="center"><span class="span">3</span></div></div>
<div id="3" style="width: 200px; height: 500px; background-color: #EE00EE"><div align="center"><span class="span">4</span></div></div>
<div id="4" style="width: 200px; height: 500px; background-color: #EEEE00"><div align="center"><span class="span">5</span></div></div>
<div id="5" style="width: 200px; height: 500px; background-color: #EE00EE"><div align="center"><span class="span">6</span></div></div>
<div id="6" style="width: 200px; height: 500px; background-color: #DD00DD"><div align="center"><span class="span">7</span></div></div>
<div id="7" style="width: 200px; height: 500px; background-color: #DDDD00"><div align="center"><span class="span">8</span></div></div>
<div id="8" style="width: 200px; height: 500px; background-color: #00DD00"><div align="center"><span class="span">9</span></div></div>
<div id="info" style="position: fixed; bottom: 0px; right: 0px; font-size: 30pt; width: auto; height: auto; background-color: #AAAAAA"></div>
</body>
<script type="text/javascript">
var positions = [];
for (var i = 0; i < 9; i++) {
var div = document.getElementById(i.toString());
console.log(div.scrollWidth)
positions.push([div.offsetLeft, div.offsetTop, div.clientWidth, div.clientHeight]);
}
console.log(positions)
</script>
</html>
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