预览待上传的本地图片

<form name="form5" id="form5" method="post" action="#">
    <input type="file" name="file5" id="file5" 
    onchange="preview5()"/>
</form>
<script type="text/javascript">
function preview5(){
  var x = document.getElementById("file5");
  if(!x || !x.value) return;
  var patn = /\.jpg$|\.jpeg$|\.gif$/i;
  if(patn.test(x.value)){
    var y = document.getElementById("img5");
    if(y){
      y.src = "file://localhost/" + x.value;
    }else{
      var img=document.createElement("img");
      img.setAttribute("src","file://localhost/"+x.value);
      img.setAttribute("width","120");
      img.setAttribute("height","90");
      img.setAttribute("id","img5");
      document.getElementById("form5").appendChild(img);
    }
  }else{
    alert("您选择的似乎不是图像文件。");
  }
}
</script>