用file标签实现多图文件上传预览

效果图：

js 代码：

<script>  
    //下面用于多图片上传预览功能
    function setImagePreviews(avalue) {
        var docObj = document.getElementById("files");
        var dd = document.getElementById("preview");
        dd.innerHTML = "";
        var fileList = docObj.files;
        for (var i = 0; i < fileList.length; i++) {
            dd.innerHTML += "<div style='float:left' > <img id='img" + i + "'  /> </div>";
            var imgObjPreview = document.getElementById("img"+i);
            if (docObj.files && docObj.files[i]) {
                //火狐下，直接设img属性
                imgObjPreview.style.display = 'block';
                //控制缩略图大小
                imgObjPreview.style.width = '70px';
                imgObjPreview.style.height = '70px';
                //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[i]);
            }
            else {
                //IE下，使用滤镜
                docObj.select();
                var imgSrc = document.selection.createRange().text;
                alert(imgSrc)
                var localImagId = document.getElementById("img" + i);
                //必须设置初始大小
                localImagId.style.width = "70px";
                localImagId.style.height = "70px";
                //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!");
                    return false;
                }
                imgObjPreview.style.display = 'none';
                document.selection.empty();
            }
        }
        return true;
    }
    </script>

HTML代码：

<form method="post" enctype="multipart/form-data">            
            <input type="file"  accept="image/png,image/gif,image/jpg,image/jpeg" id="files" name="files" multiple  onchange="javascript:setImagePreviews();" />
            <input type="button"  id="upload" value="上传" />
            <div id="preview">              
            </div>  
</form>

文章参考：http://www.jq22.com/jquery-info833