How to resolve timeStamp.getDate is not a function

So I am trying to use Javascript timestamp to relative time, So I stumbled onto this code below, which helps.

function timeSince(timeStamp){
    var now = new Date(),
      secondsPast = (now.getTime() - timeStamp) / 1000;
    if (secondsPast < 60) {
      return parseInt(secondsPast) + 's';
    }
    if (secondsPast < 3600) {
      return parseInt(secondsPast / 60) + 'm';
    }
    if (secondsPast <= 86400) {
      return parseInt(secondsPast / 3600) + 'h';
    }
    if (secondsPast > 86400) {
      day = timeStamp.getDate();
      month = timeStamp.toDateString().match(/ [a-zA-Z]*/)[0].replace(" ", "");
      year = timeStamp.getFullYear() == now.getFullYear() ? "" : " " + 
      timeStamp.getFullYear();
      return day + " " + month + year;
    }
  }

const currentTimeStamp = new Date().getTime();
console.log(timeSince(currentTimeStamp));

But when am having a timeStamp more than 24hours or a timestamp like this

const currentTimeStamp = '1659377138217';
console.log(timeSince(currentTimeStamp));

It throws an error showing TypeError: timeStamp.getDate is not a function

Please how can I solve this issue?

>Solution :

const currentTimeStamp = '1659377138217';
console.log(timeSince(currentTimeStamp));

currentTimeStamp is a string here, it must be converted to a date object to access date methods such as getDate(), try this:

const currentTimeStamp = new Date(parseInt('1659377138217'));
console.log(timeSince(currentTimeStamp));