<html>
<head>
<script src="https://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("button").click(function(){
$("p").css("border-width",function(i){
return i + 25;
});
});
});
</script>
</head>
<body>
<button>Change the border-width property of the p element</button>
<p style="border: 1px solid black;">This is a paragraph.</p>
</body>
</html>