自身迭代中嵌套Promise

loadAllUser(lastOnline, currentPage, limit, pageMax){
                //迭代自身
                //     最后在线时间   当前页数 每一页数量  页数
                var that = this;
                console.log(currentPage, eval(pageMax))
                return new Promise(resolve => {
                    if(currentPage > eval(pageMax)){//加载完毕
                        resolve({
                            err: 0,
                            msg: 'success'
                        })
                        return
                    }
                    that.loadOnePageUser(lastOnline, currentPage, limit).then(res => {
                        if(!res.err){
                            that.userList = that.userList.concat(res.userList)
                        }
                        currentPage += 1;
                        setTimeout(function(){
                            that.loadAllUser(lastOnline, currentPage, limit, pageMax).then(res => {
                                resolve(res)
                            })
                        }, 500)
                    })

                })
            }