javscript上传图片前预览的方法setPreViewImage()

<!doctype html>
<html lang="en">
 <head>
 <meta charset="UTF-8">
 <meta name="Generator" content="EditPlus?">
 <meta name="Author" content="">
 <meta name="Keywords" content="">
 <meta name="Description" content="">
 <title>Document</title>
 </head>
 <body>
 <script>
function setImagePreview() {
    var docObj = document.getElementById("doc");
    var imgObjPreview = document.getElementById("preview");
    if (docObj.files && docObj.files[0]) {
    /*火狐下，直接设img属性*/
imgObjPreview.style.display = 'block';
    imgObjPreview.style.width = '150px';
    imgObjPreview.style.height = '120px';
    /*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 = "150px";
    localImagId.style.height = "120px";
    /*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>
<input type=file name="doc" id="doc" onchange="javascript:setImagePreview();">
<p>
<div id="localImag">
<img id="preview" width=-1 height=-1 style="diplay: none" />
</div>
</p>
 </body>
</html>