电商网站购物车页面计算及HTMl更新

Question

I'm trying to build a cart page for an e-commerce website. I'm having trouble figuring out the JS for calculating.. below I'm getting a file through AJAX call called products.json which has products information like id, name, imp, prices etc and an array called productsArray which has product ids saved of products I've clicked on their respective cart icons. Now the logic is if the products.json file contains the id of products present in the array I want it to display on the cart page. So when I click the products add to cart button, for whichever product I click it gets added to local storage and from there I get it and compare it with each of the products present in the JSON file. Now this is printing my product with all furnished information. Now I want to change the price when the quantity of product is changed. I've also added a code fo that below and that too works. When I click on 2 then the price gets multiplied by 2 and showcases it in HTML. similarly for other values. The problem is this works only for the first product. I'm unable to get the functionality working for all products even though the IDs are all same.. How do I tackle this issue? Also I need to be able to access all the product prices as you can see in the second image below, sum them up then update the total on the top and the right containers under various descriptions.. How do I do these as well? Pls help. Have been trying to crack this for past 3-4 days..

 let products = new Set(); let counter = 0; // adding click events to cart icon document.body.addEventListener('click', e => { if (e.target.closest('.shopping')) { products.add(e.target.closest('.prod-card').id); // adding number of products in cart icon counter = Number(document.querySelector('#cart-badge').innerHTML) + 1; document.querySelector('#cart-badge').innerHTML = String(counter); }; // storing product ids in local storage localStorage.setItem('Products_IDs', JSON.stringify(Array.from(products))) }); // parsing JSON List for cart page let RetrievedData = localStorage.getItem("Products_IDs"); let productsArray = JSON.parse(RetrievedData); // for (i = 0; i < productsArray.length; i++){ // console.log(productsArray); // } let xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { let myProducts = JSON.parse(this.responseText); for (i = 0; i < productsArray.length; i++) { for (j = 0; j < myProducts.products.length; j++) { if (productsArray[i] == myProducts.products[j].id) { let ReturnedHTML2 = " "; ReturnedHTML2 = `<div class="cart-items-holder" id='pdt-box'> <div class='pdt-container' id='pdt-single'> <img class='img-sweater' src="Images/${myProducts.products[j].imageName}.png" alt="Sweater Image"> <div class="pdt-text w-100"> <div class="text1"> <h6>${myProducts.products[j].name}</h6> <p class="mb-0 text-secondary">Color: Multicolor</p> <p class="mb-0 text-secondary">Seller: Indus Valley & Co</p> <div class="forms mt-xl-3 mt-lg-3 mt-md-2 mt-sm-2 d-flex justify-content-start align-items-start"> <div class="form-group"> <label class='mr-2' for="exampleFormControlSelectSize"></label> <select class="form-control" id="exampleFormControlSelectSize"> <option>Size: Onesize</option> <option>S</option> <option>M</option> <option>L</option> <option>XL</option> <option>XXL</option> </select> </div> <div class="form-group2 ml-3"> <label class='mr-2' for="exampleFormControlSelectQuantity"></label> <select class="form-control" id="exampleFormControlSelectQuantity"> <option>QTY: 1</option> <option>1</option> <option>2</option> <option>3</option> <option>4</option> </select> </div> </div> </div> <div class="text2"> <p class='pricing mb-0'>Rs.<strong id='final-price'>${myProducts.products[j].priceAfterDiscount}</strong> <del id='initial-price'>Rs.${myProducts.products[j].price}</del><span class="offer font-weight-bold ml-1">(60%Off)</span></p> <small class="text-secondary">Delivery in 4 - 6 days</small> </div> </div> </div> <div class="options"> <a class="ml-3 mr-3 text-dark font-weight-bold" id='remove-btn' href="">REMOVE</a> | <a class="ml-3 mr-3 text-dark font-weight-bold" id='wishlist-btn' href="">ADD TO WISHLIST</a> </div> </div> <br>` document.querySelector('#cart-items-area').innerHTML += ReturnedHTML2; sessionStorage.setItem("discounted_price", Number(document.getElementById('final-price').innerHTML)) document.getElementById('exampleFormControlSelectQuantity').onchange = function() { if (document.getElementById('exampleFormControlSelectQuantity').selectedIndex == 1) { price_1 = sessionStorage.getItem("discounted_price"); document.getElementById('final-price').innerHTML = price_1 * 1; } else if (document.getElementById('exampleFormControlSelectQuantity').selectedIndex == 2) { price_2 = sessionStorage.getItem("discounted_price"); document.getElementById('final-price').innerHTML = price_2 * 2; } else if (document.getElementById('exampleFormControlSelectQuantity').selectedIndex == 3) { price_3 = sessionStorage.getItem("discounted_price"); document.getElementById('final-price').innerHTML = price_3 * 3; } else if (document.getElementById('exampleFormControlSelectQuantity').selectedIndex == 4) { price_4 = sessionStorage.getItem("discounted_price"); document.getElementById('final-price').innerHTML = price_4 * 4; } else { price_default = sessionStorage.getItem("discounted_price"); document.getElementById('final-price').innerHTML = price_default; } } } } } } }; xmlhttp.open("GET", "products.json", true); xmlhttp.send();

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Answer 1

Seeing that you've spent a few days on this already. I would consider it worth spending some time to refactor the existing code to be a bit more organized: :)

• I see a lot of nested ifs and fors => extract them to separate functions
• I see a big template containing an HTML document string => separate function taking 2 arguments & returns the fully rendered html document.

If you end up looking at this code for yet another day, at least it would help if you extracted every part into its own simpler function. you can also then run each function individually to test that it does what you expect this way: :) It helps a tonne to split things up!

Right now it's all one "big monster function" in the XMLHTTPRequest handler.

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Also, there is a fair bit of repeated code in the bottom, Whenever you see this it should help guide you to where to reduce and simplify your code a bit::

if (document.getElementById('exampleFormControlSelectQuantity').selectedIndex == 1) {
    price_1 = sessionStorage.getItem("discounted_price");
    document.getElementById('final-price').innerHTML = price_1 * 1;
} else if (/*repeated code*/) {
    /* repeated code, with a single number changing 2, 3, 4... */
}

the conditional code is (almost) exactly the same, so you don't have to make the same document query for the same element in every case.

const selected_number = document.getElementById('exampleFormControlSelectQuantity').selectedIndex;

and you can re-use this like this:

if (selected_number == 1) {
    price_1 = sessionStorage.getItem("discounted_price");
    document.getElementById('final-price').innerHTML = price_1 * 1;
} else if (selected_number == 2) {
    /* repeated code, with a single number changing 2, 3, 4... */
}

but now you can also just assume the number is... the number you need inside the conditional... so you can shorten the individual number checks to a single snippet of code like this:

price = sessionStorage.getItem("discounted_price");
document.getElementById('final-price').innerHTML = price * selected_number;