Why my script keep undefined?

let menu = document.querySelector('#menu-btn');
let navbar = document.querySelector('.header .navbar');

menu.onclick = () =>{
   menu.classList.toggle('fa-times');
   navbar.classList.toggle('active');
};

window.onscroll = () =>{
   menu.classList.remove('fa-times');
   navbar.classList.remove('active');
};



  var swiper = new Swiper(".home-slider", {
    loop:true,
    navigation: {
      nextEl: ".swiper-button-next",
      prevEl: ".swiper-button-prev",
    },
 });

 


function SwipeReview(){
  var swiper = new Swiper(".reviews-slider", {
    grabCursor:true,
    loop:true,
    autoHeight:true,
    spaceBetween: 20,
    breakpoints: {
       0: {
         slidesPerView: 1,
       },
       700: {
         slidesPerView: 2,
       },
       1000: {
         slidesPerView: 3,
       },
    },
  });
}



let loadMoreBtn = document.querySelector('.packages .load-more .btn');
let currentItem = 3;

let noOfCharac = 100;
let contents = document.querySelectorAll(".description");

console.log(contents);

contents.forEach(content => {
    if(content.textContent.length < noOfCharac){
        content.nextElementSibling.style.display = "none";
    }
    else{
        let displayText = content.textContent.slice(0,noOfCharac);
        let moreText = content.textContent.slice(noOfCharac);
        content.innerHTML = `${displayText}...${moreText}`;
    }
});

function readMore(btn) {
    let post = btn.parentElement;
    post.querySelector(".dots").classList.toggle("hide");
    post.querySelector(".more").classList.toggle("hide");
    btn.textContent == "Read More" ? btn.textContent = "Read Less" : btn.textContent = "Read More";
}



let minusBtn = document.querySelector("#minus")
let plusBtn = document.querySelector("#plus")
let counterElement = document.querySelector("#counter")
console.log(counterElement);
  let counter = counterElement.value;




minusBtn.addEventListener('click', function () {
    if (counter >= 1) {
        counter--
    }
    counterElement.value = counter; 
    updateAmount()
})

plusBtn.addEventListener('click', function () {
    counter++
    counterElement.value = counter; 
    updateAmount()
})

function updateAmount() {
    let totalAmountElement = document.querySelector("#totalAmount")
    let amount = document.querySelector("#amount")
    
    totalAmount = price.textContent * counter

    totalAmountElement.textContent = totalAmount.toFixed(2)
    amount.value = totalAmount.toFixed(2)

}