自由落体运动 

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title></title>
        <style>
            #div1{
                width: 100px;
                height: 100px;
                background: red;
                position: absolute;
            }
        </style>
        <script>
            window.onload=function(){
                var oDiv=document.getElementById("div1");
                var oInput=document.getElementById("input1");
                var timer=null;
                var iSpeed=0;
                
                oInput.onclick=function(){
                    startMove();
                }
                function startMove(){
                    clearInterval(timer);
                    timer=setInterval(function(){
                        iSpeed+=3;
                        var T=oDiv.offsetTop+iSpeed;
                        if(T>document.documentElement.clientHeight-oDiv.offsetHeight){
                            T=document.documentElement.clientHeight-oDiv.offsetHeight;
                            iSpeed*=-1;
                            iSpeed*=0.75;
                        }
                        oDiv.style.top=T+"px";
                        
                    },30)
                }
            }
        </script>
    </head>
    <body>
        <input type="button" value="开始运动" id="input1" />
        <div id="div1"></div>
    </body>
</html>

 

posted @ 2019-01-09 15:04  webxy  阅读(192)  评论(0)    收藏  举报