【js】弹出文件选择框，可用与文件上传（适配所有浏览器）

<a class="btn blue mini" style="margin-bottom:6px;">导入Excel
<div style="filter:alpha(opacity=0);cursor: pointer; opacity: 0; position: absolute;  width: 75px;margin: -18px 0 0 -6px ;margin: -16px 0 0 -6px\9;height:20px\9;overflow: hidden; ">
<input type="file" id="txtFile" onchange="uploadFile()" name="upload" style="font-size: 200px;cursor: pointer;direction: rtl ！important; float: right\9; "/>
</div>
</a>