使用Math获取随机颜色

    <style>
        div{
            width: 100px;
            height: 100px;
            border:1px solid red;
        }
    </style>
    <div id="mydiv"></div>
    <script>
        //返回一个随机数的颜色
        function getColor(){
            var arr = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9", 
                        "a", "b", "c", "d", "e","f"];
            var str = "#";
            for(var i=0;i<6;i++){
                //生成0~16的随机数
                var r = parseInt(Math.random()*16);
                str += arr[r];
            }
            return str;
        }
        //根据id找到对应的页面元素
        var div = document.getElementById("mydiv");
        //修改style里面backgroundColor
        /*
           <style>
               div{
                 background-color : red;
               }
           </style>
        */
        div.style.backgroundColor = getColor();
    </script>