1.event.preventDefault()
preventDefault() 方法阻止元素发生默认的行为（例如，当点击提交按钮时阻止对表单的提交）
2.event.stopPropagation()
event.stopPropagation() 方法阻止事件冒泡到父元素，阻止任何父事件处理程序被执行。尤其是点击事件。
<!DOCTYPE html>
<html>
<head>
<script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("span").click(function(event){
event.stopPropagation();
alert("The span element was clicked.");
});
$("p").click(function(event){
alert("The p element was clicked.");
});
$("div").click(function(){
alert("The div element was clicked.");
});
});
</script>
</head>
<body>
<div style="height:100px;width:500px;padding:10px;border:1px solid blue;
background-color:lightblue;">
This is a div element.
<p style="background-color:pink">This is a p element, in the div element.
<br><span style="background-color:orange">This is a span element in the p
and the div element.</span></p></div>
</body>
</html>