improve event listeners in cart.js

public/js/cart.js

-const loaderElem = document.querySelector('.loader');
-
 class Cart {
     constructor(cartElem) {
         this.cartHtmlElem = cartElem;
@@ -48,90 +46,75 @@ class Cart {
         document.querySelector('.js-total-cart-price').textContent = 'Total € ' + this.totalPrice;
     }
 
-    setRemoveItemFromCartEventListener() {
-        this.bindedRemoveItemFromCart = removeItemFromCart.bind(this);
+    updateItemQty(event) {
+        if (!event.target.classList.contains('js-qty-input')) {
+            return;
+        }
 
-        document.querySelector('.js-cart').addEventListener('click',  this.bindedRemoveItemFromCart);
+        const changedQty = event.target.value;
+        if (!changedQty || (changedQty.indexOf('e') + 1) || changedQty === '0') {
+            event.target.value = event.target.defaultValue;
+            return;
+        }
 
-        function removeItemFromCart(event) {
-            if (!event.target.classList.contains('js-remove-btn')) return;
-            const actionUrl = event.target.dataset.action;
-            const productId = event.target.dataset.productId;
+        const actionUrl = this.updateItemUrl;
+        const productId = event.target.dataset.productId;
 
-            loaderElem.classList.toggle('loader-show');
+        loaderElem.classList.toggle('loader-show');
 
-            axios.post(actionUrl, {
-                productId: productId,
+        axios.post(actionUrl, {
+            productId: productId,
+            changedQty: changedQty,
+        })
+            .then( (response) => {
+                this.show();
+                toastr.success('Quantity updated');
             })
-                .then( (response) => {
-                    const redirectLinkWhenEmpty = response.data.redirectLinkWhenEmpty;
-                    if (redirectLinkWhenEmpty) {
-                        window.location.replace(redirectLinkWhenEmpty);
-                        return;
-                    }
-
-                    this.removeEventListeners();
-                    this.show();
-                    loaderElem.classList.toggle('loader-show');
-                    toastr.success('Product deleted');
-                })
-                .catch(function (error) {
-                    console.log(error);
-                    loaderElem.classList.toggle('loader-show');
-                    toastr.error('Error, something went wrong');
-                });
-        }
+            .catch(function (error) {
+                console.log(error);
+                loaderElem.classList.toggle('loader-show');
+                toastr.error('Error, something went wrong');
+            });
     }
 
-    setUpdateItemQtyEventListener() {
-        this.bindedUpdateItemQty = bindedUpdateItemQty.bind(this);
-
-        document.querySelector('.js-cart').addEventListener('change', this.bindedUpdateItemQty);
-
-        function bindedUpdateItemQty(event) {
-            if (!event.target.classList.contains('js-qty-input')) return;
-
-            const changedQty = event.target.value;
-            if (!changedQty || (changedQty.indexOf('e') + 1) || changedQty === '0') {
-                event.target.value = event.target.defaultValue;
-                return;
-            }
-
-            const actionUrl = this.updateItemUrl;
-            const productId = event.target.dataset.productId;
+    removeItemFromCart(event) {
+        if (!event.target.classList.contains('js-remove-btn')) {
+            return;
+        }
+        const actionUrl = event.target.dataset.action;
+        const productId = event.target.dataset.productId;
 
-            loaderElem.classList.toggle('loader-show');
+        loaderElem.classList.toggle('loader-show');
 
-            axios.post(actionUrl, {
-                productId: productId,
-                changedQty: event.target.value,
+        axios.post(actionUrl, {
+            productId: productId,
+        })
+            .then( (response) => {
+                const redirectLinkWhenEmpty = response.data.redirectLinkWhenEmpty;
+                if (redirectLinkWhenEmpty) {
+                    window.location.replace(redirectLinkWhenEmpty);
+                    return;
+                }
+                this.show();
+                toastr.success('Product deleted');
             })
-                .then( (response) => {
-                    this.removeEventListeners();
-                    this.show();
-                    loaderElem.classList.toggle('loader-show');
-                    toastr.success('Quantity updated');
-                })
-                .catch(function (error) {
-                    console.log(error);
-                    loaderElem.classList.toggle('loader-show');
-                    toastr.error('Error, something went wrong');
-                });
-        };
-    }
-
-    removeEventListeners() {
-        this.cartHtmlElem.removeEventListener('change', this.bindedUpdateItemQty);
-        this.cartHtmlElem.removeEventListener('click', this.bindedRemoveItemFromCart);
+            .catch(function (error) {
+                console.log(error);
+                loaderElem.classList.toggle('loader-show');
+                toastr.error('Error, something went wrong');
+            });
     }
 
     events() {
-        this.setRemoveItemFromCartEventListener();
-        this.setUpdateItemQtyEventListener();
+        this.cartHtmlElem.addEventListener('change', this.updateItemQty.bind(this));
+        this.cartHtmlElem.addEventListener('click', this.removeItemFromCart.bind(this));
+        this.hasEvents = true;
     }
 
     show() {
-        loaderElem.classList.toggle('loader-show');
+        if (!loaderElem.classList.contains('loader-show')) {
+            loaderElem.classList.toggle('loader-show');
+        }
 
         axios.get(this.getItemsUrl)
             .then( response => {
@@ -150,7 +133,10 @@ class Cart {
 
                 this.showProducts();
                 loaderElem.classList.toggle('loader-show');
-                this.events();
+
+                if (!this.hasEvents) {
+                    this.events();
+                }
             })
             .catch(function (error) {
                 console.log(error);
@@ -160,7 +146,8 @@ class Cart {
     }
 }
 
-const cartElem = document.querySelector('.js-cart');
+const loaderElem = document.querySelector('.loader');
 
+const cartElem = document.querySelector('.js-cart');
 const cart = new Cart(cartElem);
 cart.show();