js 请求单个文件 并验证扩展名

function suffix(file_name) {
var three=file_name.split(".");
var last=three[three.length-]; return last;
}
$('#btnSearch').click(function(){
fileElem = document.getElementById("fileElem");
fileElem.click();
}); var test =false;
$('#btnImport').click(function () {
fileElem = document.getElementById("fileElem");
var name = suffix(fileElem.files[].name); if (name.toLowerCase() != "AVI".toLowerCase()) { //判断大小写
layer.msg("文件类型不对!");
return false;
}
if (fileElem.files.length == ) {
layer.msg("文件不能为空!");
return false;
}
// 实例化一个表单数据对象
var uploadFile = new FormData();
uploadFile.append("A4", fileElem.files[]);
uploadFile.append("Menuid",@ViewBag.id);
if(test==false){
test= true;
if ("undefined" != typeof (uploadFile) && uploadFile != null && uploadFile != "") {
$.ajax({
url: '/Backstage/',
type: 'POST',
data: uploadFile,
async: false,
cache: false,
contentType: false, //不设置内容类型
processData: false, //不处理数据
success: function (data) {
layer.msg(data.msg);;
setTimeout(function () {
test = !test;
window.location.href = "/Backstage/";
}, );
//console.log(data);
},
error: function () {
layer.msg("导入失败!");;
}
})
} else {
layer.msg("选择的文件无效！请重新选择");
}
} });

var arrEx = ["jpeg","jpg","png","gif"];
$('#btnImport').click(function () {
var flag = false; //状态
fileElem = document.getElementById("fileElem");
var name = suffix(fileElem.files[0].name);
//循环比较
for(var i=0;i<arrEx.length;i++)
{
if(name.toLowerCase() == arrEx[i])
{
flag = true; //一旦找到合适的，立即退出循环
break;
}
}
if (!flag) {
layer.msg("文件类型不对!");
return false;
}

string exName = System.IO.Path.GetExtension(file.FileName); //得到扩展名
var arrEx =new []{ "jpeg", "jpg", "png", "gif" };
var flag = false; //状态
//循环比较
for (var i = ; i < arrEx.Length; i++)
{
if (exName.ToLower() == arrEx[i])
{
flag = true; //一旦找到合适的，立即退出循环
break;
}
}
if (!flag) //没有找到
{
return Json(new { msg = "文件类型不对!" });
}