JS if timer reaches 0 add +7 days

If the timer reaches 0 how to add +7 days instead of writing “end of timer”

    <script>
    var endDate = new Date("Jan 25, 2020 12:00:00").getTime();
    var timer = setInterval(function () {
    let now = new Date().getTime();
    let t = endDate - now;
    if (t >= 0) {
    document.getElementById("remainder").innerHTML =
    Math.floor(t / (1000 * 60 * 60 * 24)) + "DAY(S) " +
    ("0" + Math.floor((t % (1000 * 60 * 60 * 24)) / (1000 * 60 * 60))).slice(-2) + "HR(S) " +
    ("0" + Math.floor((t % (1000 * 60 * 60)) / (1000 * 60))).slice(-2) + "MIN(S) " +
    ("0" + Math.floor((t % (1000 * 60)) / 1000)).slice(-2) + "SEC(S)";
    } else {
    document.getElementById("remainder").innerHTML = "End of timer.";
    }
    
    }, 1000);
    </script>
endDate.setDate(endDate.getDate() + 7);
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