subline/views/shared/banner.ejs

<div class="banner">
    <ul></ul>
</div>

<script>
    let banner = {
        errorList: [],
        notificationList: [],

        createNotification: function(value){
            this.notificationList.push(value);

            this.updateNotifications();

            setTimeout(()=>{
                this.notificationList.splice(0, 1);
                this.updateNotifications();
            }, 10000);
        },

        createError: function(value){
            this.errorList.push(value);

            this.updateNotifications();

            setTimeout(()=>{
                this.errorList.splice(0, 1);
                this.updateNotifications();
            }, 10000);
        },

        updateNotifications: function(){
            let ul = document.querySelector(".banner ul");

            while(ul.hasChildNodes()){
                ul.removeChild(ul.firstChild);
            }

            for(let notification of this.notificationList){
                let li = document.createElement("li");
                li.classList = "notification";
                li.innerText = notification;
                ul.appendChild(li);
            }

            for(let error of this.errorList){
                let li = document.createElement("li");
                li.classList = "error";
                li.innerText = error;
                ul.appendChild(li);
            }
        }
    }
</script>