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							- <!DOCTYPE html>
 
- <html lang="en">
 
- <head>
 
-   <meta charset="UTF-8">
 
-   <meta http-equiv="X-UA-Compatible" content="IE=edge">
 
-   <meta name="viewport" content="width=device-width, initial-scale=1.0">
 
-   <title>Document</title>
 
-   <style>
 
-     * {
 
-       margin: 0;
 
-       padding: 0;
 
-     }
 
-     #div1 {
 
-       width: 200px;
 
-       height: 200px;
 
-       background: red;
 
-       transition: width 2s linear;
 
-     }
 
-   </style>
 
- </head>
 
- <body>
 
-   <button id="up">放大</button>
 
-   <div id="div1"></div>
 
-   <button id="down">缩小</button>
 
-   <script>
 
-     var up = document.getElementById('up')
 
-     var down = document.getElementById('down')
 
-     var div1 = document.getElementById('div1')
 
-     // up.onclick = function () {
 
-     //   var timer = setInterval(function () {
 
-     //     if (div1.offsetWidth < 500) {
 
-     //       div1.style.width = div1.offsetWidth + 10 + 'px'
 
-     //     } else {
 
-     //       clearInterval(timer)
 
-     //     }
 
-     //   }, 10);
 
-     //   // div1.style.width = 500 + 'px'
 
-     // }
 
-     up.onclick = function () {
 
-       div1.style.width = 500 + 'px'
 
-     }
 
-     down.onclick = function () {
 
-       var timer1 = setInterval(function () {
 
-         if (div1.offsetWidth > 0) {
 
-           div1.style.width = div1.offsetWidth - 10 + 'px'
 
-         } else {
 
-           clearInterval(timer1)
 
-         }
 
-       }, 10)
 
-     }
 
-   </script>
 
- </body>
 
- </html>
 
 
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