screenshots.gif

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin:0;
            padding:0;
        }
        .box{
            position:absolute;
            top:100px;
            left:0;
            width:100px;
            height:100px;
            background-color:skyblue;
        }

    </style>
</head>
<body>

    <input type="button" value="开始将下面的元素向右移动" id="start">
    <div class="box" id="box">

    </div>

    <script>
        var start = document.getElementById("start");
        var box = document.getElementById("box");
        //点击开始按钮，让box向右运动
        //全局变量存储left的属性值，会每次发生变化
        //信号量，初始值必须与属性初始值保持一致
        var nowleft = 0;
        //定时器，制作运动过程
start.onclick = function(){

        setInterval(function(){
            //信号量进行自加
            nowleft += 1;
            //将最新的nowleft的值赋值给元素的css属性
            box.style.left = nowleft + "px";


        },100);
        
    };
    </script>
    
</body>
</html>
    <!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Document</title>
        <style>
            *{
                margin:0;
                padding:0;
            }
            .box{
                position:absolute;
                top:100px;
                left:0;
                width:100px;
                height:100px;
                background-color:skyblue;
            }
    
        </style>
    </head>
    <body>
    
        <input type="button" value="开始将下面的元素向右移动" id="start">
        <div class="box" id="box">
    
        </div>
    
        <script>
            var start = document.getElementById("start");
            var box = document.getElementById("box");
            //点击开始按钮，让box向右运动
            //全局变量存储left的属性值，会每次发生变化
            //信号量，初始值必须与属性初始值保持一致
            var nowleft = 0;
            //定时器，制作运动过程
    start.onclick = function(){
    
            setInterval(function(){
                //信号量进行自加
                nowleft += 1;
                //将最新的nowleft的值赋值给元素的css属性
                box.style.left = nowleft + "px";
    
    
            },100);
            
        };
        </script>
        
    </body>
    </html>