How to use javascript/jquery in Reactjs

I am working in Reactjs and i am using nextjs framework,Right now i am trying to use following code in index.js so i can display data (day month day etc),How can i do this ? Here is my code

<script>
function updateTimer() {
  future  = Date.parse("June 11, 2020 11:30:00");
  now     = new Date();
  diff    = future - now;

  days  = Math.floor( diff / (1000*60*60*24) );
  hours = Math.floor( diff / (1000*60*60) );
  mins  = Math.floor( diff / (1000*60) );
  secs  = Math.floor( diff / 1000 );

  d = days;
  h = hours - days  * 24;
  m = mins  - hours * 60;
  s = secs  - mins  * 60;
  document.getElementById("timer")
    .innerHTML =
      '<div>' + d + '<span>days</span></div>' +
      '<div>' + h + '<span>hours</span></div>' +
      '<div>' + m + '<span>minutes</span></div>' +
      '<div>' + s + '<span>seconds</span></div>' ;
}
setInterval('updateTimer()', 1000 );

</script>
<div id="timer"></div>