自定义一个的参数写法： 

<el-upload :on-success="handleAvatarSuccess($event,1)}"> //这里必须是$event，是个回调函数$event代表拿原本传进来的参数
</el-upload>
 
handleAvatarSuccess(res, flag){ 
	console.log('1',res,flag)
},


<el-upload :on-success="(val) =>{handleAvatarSuccess(val,1)}"> //这里可以任意，原本的就是给一个参数接受，然后我想要执行某个方法
</el-upload>
 
handleAvatarSuccess(res, flag){ //通过flag接收传过来的1
	console.log('1',res,flag)
},

 自定义多个的参数写法： 

<el-upload :on-success="(...event) =>{handleAvatarSuccess(event, 1)}"> //这里可以任意字段
</el-upload>
 
handleAvatarSuccess(param, flag){ //接收到数组
    let res = param[0]
	let file = param[1]
	console.log('res', res)
},