input[type=file]文件获取及ajax上传

var formData = new FormData();
formData.append('file', $('#imgfile')[0].files[0]);
$.ajax({
		 url: 'updatebannerimg?id='+lineid,
		 type: 'POST',
		 cache: false,
		 data: formData,
		 processData: false,
		 contentType: false
		}).done(function(res) {
			document.location.href='bannerlist';
		}).fail(function(res) {

		});		

<input type="file" name="imgfile" id="imgfile" />