利用JavaScript实现图片上传预览

html代码：

<div class="col-xs-12">
  <div class="col-xs-12">
    <!-- PAGE CONTENT BEGINS -->

    <form action="" method="post" class="form-horizontal" role="form" enctype="multipart/form-data" method="post">
        <div class="form-group">
            <label class="col-sm-3 control-label no-padding-right" for="form-field-1"></label>
            <div class="col-sm-9" id="localImag">
                <img class="editable img-responsive editable-click editable-empty" id="preview" src="" style="display: block;" />
            </div>
        </div>
        <div class="form-group">
            <label class="col-sm-3 control-label no-padding-right" for="form-field-1"> 头像 </label>

            <div class="col-sm-9">
                 <input type="file" name="img" id="doc" multiple="multiple" onchange="javascript:setImagePreview();">
            </div>
        </div>
        <div class="clearfix form-actions">
            <div class="col-md-offset-3 col-md-9">
                <button class="btn btn-info" type="submit">
                    <i class="icon-ok bigger-110"></i>
                    添加
                </button>

                &nbsp; &nbsp; &nbsp;
                <button class="btn" type="reset">
                    <i class="icon-undo bigger-110"></i>
                    重置
                </button>
            </div>
        </div>
    </form>
</div>

js代码：

<script type="text/javascript">
            //下面用于图片上传预览功能
            function setImagePreview(avalue) {
            //input
                var docObj = document.getElementById("doc");
//img
                var imgObjPreview = document.getElementById("preview");
                //div
                var divs = document.getElementById("localImag");
                if (docObj.files && docObj.files[0]) {
                    //火狐下，直接设img属性
                    imgObjPreview.style.display = 'block';
                    imgObjPreview.style.width = '100px';
                    imgObjPreview.style.height = '100px';
                    //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 = "100px";
                    localImagId.style.height = "100px";
                    //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>

效果预览：