$('#regenerateOTP').on('click', function () {
  disableResend();
  timer(120);
        $.ajax({
            url: baseUrl + "index.php/request/sendOTP",
            type: 'post',
            data: { contactNo: $("#txtCustomerContactUpdate").val() },
            success: function (data) {
                swal({ title: "Sweet!", text: "One time password Message is sent again", timer: 2000, imageUrl: "../images/thumbs-up.jpg" });
            },
            error: function () {
                swal({ title: "Error!", text: "We are facing technical error!", type: "error", timer: 2000, confirmButtonText: "Ok" });
                return false;
            }
        });

    });

function disableResend()
{
 $("#regenerateOTP").attr("disabled", true);
 timer(60);
  //$('.regenerateOTP').prop('disabled', true);
  setTimeout(function() {
    // enable click after 1 second
 $('#regenerateOTP').removeAttr("disabled");
    //$('.disable-btn').prop('disabled', false);
  }, 60000); // 1 second delay
}

let timerOn = true;

function timer(remaining) {
  var m = Math.floor(remaining / 60);
  var s = remaining % 60;
  
  m = m < 10 ? '0' + m : m;
  s = s < 10 ? '0' + s : s;
  document.getElementById('timer').innerHTML = m + ':' + s;
  remaining -= 1;
  
  if(remaining >= 0 && timerOn) {
    setTimeout(function() {
        timer(remaining);
    }, 1000);
    return;
  }

  if(!timerOn) {
    // Do validate stuff here
    return;
  }
  
  // Do timeout stuff here
  alert('Timeout for otp');
}

<input type="text" name="otp" placeholer="Enter your otp"/>

<button id="regenerateOTP" class="btn btn-warning btn_shadow" style="border-radius: 0;" >Resend OTP </button> 
<div>Time left = <span id="timer"></span></div>