JS实现本地图片预览

代码：

<script>
function setImagePreview(localImag,doc,imgId) {
        var docObj=document.getElementById(doc);
        var imgObjPreview=document.getElementById(imgId);
                if(docObj.files &&    docObj.files[0]){
                        //火狐下，直接设img属性
                        imgObjPreview.style.display = 'block';
                        imgObjPreview.style.width = '128px';
                        imgObjPreview.style.height = '128px';                    
                        //imgObjPreview.src = docObj.files[0].getAsDataURL();
 
      //火狐7以上版本不能用上面的getAsDataURL()方式获取，需要一下方式  
      imgObjPreview.src = window.URL.createObjectURL(docObj.files[0]);
 
                }else{
                        //IE下，使用滤镜
                        docObj.select();
                        var imgSrc = document.selection.createRange().text;
                        var localImagId = document.getElementById(localImag);
                        //必须设置初始大小
                        localImagId.style.width = "128px";
                        localImagId.style.height = "128px";
                        //图片异常的捕捉，防止用户修改后缀来伪造图片
                        try{
                                localImagId.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
                                localImagId.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;
                        }catch(e){
                                alert("您上传的图片格式不正确，请重新选择!");
                                    docObj.select();    
                                    document.execCommand("delete");
                                return false;
                        }
                        imgObjPreview.style.display = 'none';
                        document.selection.empty();
                }
                return true;
        }
</script>
<div id="localImag">
    <img id="imgId" />
</div>

<input name="image" type="file" id="doc" onchange="javascript:setImagePreview('localImag','doc','imgId');">