比较平滑的js控制textaera的高度

<meta http-equiv="content-type" content="text/html; charset=utf-8"> <title>佐佐制造 --textarea---addheight</title> <style type="text/css"> /* reset style */ * { margin:0; padding:0; word-break:break-all; } body { background:#fff; color:#333; font:12px/1.4em helvetica, arial, sans-serif; } h1, h2, h3, h4, h5, h6 { font-size:1em; } a { color:#333; text-decoration:none; } a:hover { text-decoration:underline; } ul, li { list-style:none; } fieldset, img { border:none; } input, textarea, select, button { font:12px helvetica, arial, sans-serif; } .button { padding:0 10px; height: 22px; border: 1px solid; border-color: #eee #999 #999 #eee; background: #ddd; color: #333; line-height: 20px; cursor: pointer; margin-left:2px; } .submit { padding:0 10px; height: 22px; border: 1px solid; border-color: #ddd #cc8305 #cc8305 #ddd; background: #ffa200; color: #fff; line-height: 20px; letter-spacing: 1px; cursor: pointer; } /* edit style */ #edit { width:300px; margin:50px; } .edit_caption { width:100%; overflow:hidden; margin-bottom:1px; overflow:hidden; } .edit_caption span { display:block; float:left; margin:0 1px; padding:4px 10px; background:#ddd; cursor:pointer; } .edit_caption span:hover { background:#eee; } #edit textarea { width:300px; height:80px; margin:0; padding:0; } </style> <div id="edit"> <div class="edit_caption"> <span class="tool_bigger" onclick="addheight()">放大</span> <span class="tool_smaller" onclick="minheight()">缩小</span> </div> <div><textarea id="comment_content" tabindex="1" rows="8" name="comment_content" style="height:100px">/textarea>