ajax上传前/完成后的优化操作

$.ajax({
	type : \'post\',
	url : \'upimg\', //接口
	data : formdata,
	cache : false,
	processData : false, // 不处理发送的数据，因为data值是Formdata对象，不需要对数据做处理
	contentType : false, // 不设置Content-type请求头
	success: function(data){
		if(data.code==\'0\')
		{
			var img_url = \'../../uploads/\'+data.img_name;
			var html = \'<div style=\"position: relative;margin:15px 15px 15px 0;width:45%;display: inline-block;border: 1px solid #CCC;background:#EEE;\">\'
				+\'<span style=\"display: block;width:91%;height:91%;border: 1px solid #F2F1F0;margin: 5px;overflow: hidden;\">\'
				+\'<img src=\"\'+img_url+\'\" style=\"width: 100%;\" />\'
				+\'</span>\'
				+\'<input type=\"hidden\" name=\"imgs[]\" value=\"\'+data.img_name+\'\" />\'
				+\'<a onclick=\"delImg(this);\" style=\"z-index: 10;display: block;top: -8px;cursor:pointer;right: -8px;position:absolute;width: 20px;height: 20px;background: #CCC;border-radius:100%;text-align:center;line-height: 20px;border: 1px solid #C1C1C1;color: #555;\">X</a>\'
				+\'</div>\';
			$(\'#img-list-box\').append(html);
		}else{
			layer.msg(data.msg, {icon:2,time:1000});
		}	
	},
	error: function(XmlHttpRequest, textStatus, errorThrown){
		layer.msg(\'上传出错\', {icon:2,time:1000});
	},
	beforeSend: function(){
		// 禁用按钮防止重复提交
		$(\"#up-img-file\").attr(\"disabled\",true);
		$(\"#add-img\").text(\"上传中\");
	},
	complete: function(){
		$(\"#up-img-file\").attr(\"disabled\",false);
		$(\"#add-img\").text(\"添加\");
	},
});