测试环境:

OS --> winXP

Browsers --> IE6+, FF 3.0.11, FF 3.5, Opera 9.64, Opera 10 beta 2, Safari 4, Chrome 2.0.172

xhtml:

<input type="file" value="选择文件" id="fileInput" />

<button type="button" id="btnClear">清空文件域</button>

JS:

<script type="text/javascript">

     var btn = document.getElementById("btnClear");

     var file = document.getElementById("fileInput");

     btn.onclick = function() {

         // for IE, Opera, Safari, Chrome

         if (file.outerHTML) {

             file.outerHTML = file.outerHTML;

         } else { // FF(包括3.5)

             file.value = "";

         }

    }

</script>