var attendance={
    students:[],
    total:6,
    join:function(name){
        this.students.push(name)
        console.log(this.students)
        if(this.students.length===this.total){
            console.log(name+"到课,学生已经全部到齐")
        }else{
            console.log(name+"到课,学生已经未到齐")
        }
    },
    leave:function(name){
        var idx=this.students.indexOf(name)
        if(idx!==-1){
            this.students.splice(idx,1)
        }
        console.log(name+"早退")
        console.log(this.students)
    }
}
attendance.join("歌谣")
attendance.join("方方")
attendance.join("康康")
attendance.leave("轩轩")