折翼天使表现特性二：位置跟随，CSS深入理解之absolute教程-慕课网

index.html
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>折翼天使表现特性二：位置跟随</title>
<style>
input[type=button] {
    height: 32px;
    font-size: 100%;
}
p { margin-left: 260px; }
img + p { margin-top: 60px; }
</style>
</head>
 
<body>
<img src="http://img1.sycdn.imooc.com//54447b06000171a002560191.jpg">
<div><img src="http://img1.sycdn.imooc.com//54447f4a0001eb7d01910256.jpg"></div>
<img src="http://img1.sycdn.imooc.com//54447f550001ccb002560191.jpg">
<p><input type="button" id="block" value="点击第2张图片应用display:block"></p>
<p><input type="button" id="button" value="点击第2张图片应用position:absolute变天使"></p>
<script>
var block = document.getElementById("block"),
    button = document.getElementById("button"),
    image2 = document.getElementsByTagName("img")[1];
if (block && button && image2) {
    var value_init_button = button.value;
	button.onclick = function() {
		if (this.value == value_init_button) {
			image2.style.position = "absolute";
			this.value = "撤销";
		} else {
			image2.style.position = "";
			this.value = value_init_button;
		}
	};
 
	var value_init_block = block.value;
	block.onclick = function() {
		if (this.value == value_init_block) {
			image2.style.display = "block";
			this.value = "撤销";
		} else {
			image2.style.display = "";
			this.value = value_init_block;
		}	
	};
}
</script>
</body>
</html>
折翼天使表现特性二：位置跟随

任务
