JS-简单地匀速运动框架

<!DOCTYPE html>
<html>

    <head>
        <meta charset="UTF-8">
        <title>运动框架-匀速运动</title>
        <style type="text/css">
            .div {
                width: 100px;
                height: 100px;
                background-color: chartreuse;
                margin-top: 20px;
                position: relative;
                left: 0;
                top: 0;
            }
        </style>
        <script type="text/javascript">
            var timer = null;
            function start() {
                var oBtn = document.getElementById('btn');
                var oDiv = document.getElementById('div');
                //1
                clearInterval(timer);
                timer = setInterval(function() {
                    var speed = 1;
                    //2
                    if(oDiv.offsetLeft >= 1100) {
                        clearInterval(timer);
                    }
                    else{
                        oDiv.style.left = oDiv.offsetLeft + speed + 'px';
                    }
                    
                }, 30)
            }
        </script>
    </head>

    <body>
        <input type="button" id="btn" value="运动" onclick="start()" />
        <div class="div" id="div"></div>
        <p>关键点:1:清除定时器，2：if/else判断</p>
    </body>

</html>

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