点击时扩散效果

 
<style>
p {
    margin: 0;
    position: relative;
    padding: 60px 30px;
    background-color: orange;
    color: #fff;
    width: 200px;
    overflow: hidden;
    text-align: center;
    border: 20px solid #000;
}

i {
    position: absolute;
    width: 520px;
    height: 520px;
    border-radius: 50%;
}
</style>

<p><i></i></p>

<script src="http://code.jquery.com/jquery-1.11.3.min.js"></script>
    <script>
    (function() {
        var key = true;
        $("p").click(function(event) {
            var e = event || window.event;
            if (key) {
                key = false;
                var scale = 0;
                var a = 0.8;
                var timer = setinterval(function() {
                    if (scale >= 1 || a <= 0) {
                        scale = 0;
                        a = 0.8;
                        clearinterval(timer);
                        key = true;
                    }
                    $("i").css({
                        "left": e.pagex - 8 - 20,
                        "top": e.pagey - 8 - 20,
                        "transform": "translate(-50%,-50%) scale(" + scale + ")",
                        "background-color": "rgba(225,225,225," + a + ")"
                    });
                    scale += 0.01;
                    a -= 0.008;
                }, 10)
            }
        })
    }())
</script>