js判断文件类型大小并给出提示

<form id="uploadForm" method="post" class="layui-form">
<div class="layui-form-item">
<label class="layui-form-label">名称</label>
<div class="layui-input-block">
<input type="text" name="name" required lay-verify="required"
placeholder="请输入文件名" autocomplete="off" class="layui-input">
</div>
</div> <div class="layui-form-item">
<label class="layui-form-label">资料类型:</label>
<div class="layui-input-block">
<select name="datatypeid" id="datatypeid"></select>
</div>
<input type="hidden" id="yincang">
</div>
<div class="layui-form-item">
<label class="layui-form-label">上传文件</label> <div class="layui-input-block">
<input class="layui-input" type="file" name="file" onchange="fileChange(this);"/>
</div>
</div> <div class="layui-form-item">
<div class="layui-input-block"> <input type="button" class="layui-btn" value="上传"
onclick="upload()" />
</div>
</div>
</form>

<script type="text/javascript">
var isIE = /msie/i.test(navigator.userAgent) && !window.opera;
function fileChange(target, id) {
var fileSize = 0;
var filetypes = [ ".doc", ".docx" ];//这里设置接受的文件类型
var filepath = target.value;
var filemaxsize = 1024 * 10;//接受的文件最大10M
if (filepath) {
var isnext = false;
var fileend = filepath.substring(filepath.indexOf("."));
if (filetypes && filetypes.length > 0) {
for (var i = 0; i < filetypes.length; i++) {
if (filetypes[i] == fileend) {
isnext = true;
break;
}
}
}
if (!isnext) {
alert("不接受此文件类型！");
target.value = "";
return false;
}
} else {
return false;
}
if (isIE && !target.files) {
var filePath = target.value;
var fileSystem = new ActiveXObject("Scripting.FileSystemObject");
if (!fileSystem.FileExists(filePath)) {
alert("附件不存在，请重新输入！");
return false;
}
var file = fileSystem.GetFile(filePath);
fileSize = file.Size;
} else {
fileSize = target.files[0].size;
} var size = fileSize / 1024;
if (size > filemaxsize) {
alert("附件大小不能大于" + filemaxsize / 1024 + "M！");
target.value = "";
return false;
}
if (size <= 0) {
alert("附件大小不能为0M！");
target.value = "";
return false;
}
}
</script>