ajax.js

var msgCheck = setInterval(fetch, 5e3);
function fetch() {
    var n = new XMLHttpRequest;
    n.onreadystatechange = function(e) {
        if (4 == this.readyState && 200 == this.status) {
            var t = JSON.parse(n.responseText);
            console.log(t),
            addtoDOM(t)
        }
    }
    ,
    n.open("GET", "/api/posts", !0),
    n.send()
}
function addtoDOM(e) {
    var t = [];
    $("#Data-table tr").each(function() {
        t.push(this.id)
    });
    for (var n = 0; n < e.length; n++)
        t.includes(e[n]._id) || insertNewRow(e[n], e.length)
}
function insertNewRow(e, t) {
    var n = document.getElementById("Data-table").insertRow(1);
    n.id = e._id;
    var s = n.insertCell(0)
      , a = n.insertCell(1)
      , i = n.insertCell(2);
    s.innerHTML = e.theMessage,
    a.innerHTML = e.username,
    i.innerHTML = "Just now"
}