Javascript 总计在购物车中显示NaN
所以我现在面临的问题是这个。我在CartContext中有一个Cart逻辑。除了位于Checkout组件中的total之外,所有东西都可以工作,它应该合计购物车中所有商品的价格,但实际上是显示NAN。这里是指向CodeSandbox的链接,如果sandbox出现问题,可以更好地理解注释 购物车上下文Javascript 总计在购物车中显示NaN,javascript,json,reactjs,commerce,Javascript,Json,Reactjs,Commerce,所以我现在面临的问题是这个。我在CartContext中有一个Cart逻辑。除了位于Checkout组件中的total之外,所有东西都可以工作,它应该合计购物车中所有商品的价格,但实际上是显示NAN。这里是指向CodeSandbox的链接,如果sandbox出现问题,可以更好地理解注释 购物车上下文 import React from "react"; function getCartFromLocalStorage() { return localStorage.get
import React from "react";
function getCartFromLocalStorage() {
return localStorage.getItem("cart")
? JSON.parse(localStorage.getItem("cart"))
: [];
}
const CartContext = React.createContext();
function CartProvider({ children }) {
const [cart, setCart] = React.useState(getCartFromLocalStorage());
const [total, setTotal] = React.useState(0);
const [cartItems, setCartItems] = React.useState(0);
React.useEffect(() => {
localStorage.setItem("cart", JSON.stringify(cart));
let newTotal = cart.reduce((total, cartItem) => {
return (total += cartItem.amount * cartItem.price);
}, 0);
newTotal = parseFloat(newTotal.toFixed(2));
setTotal(newTotal);
// cart items
let newCartItems = cart.reduce((total, cartItem) => {
return (total += cartItem.amount);
}, 0);
setCartItems(newCartItems);
}, [cart]);
// global functions
const removeItem = id => {
setCart([...cart].filter(item => item.id !== id));
};
const increaseAmount = id => {
const newCart = [...cart].map(item => {
return item.id === id
? { ...item, amount: item.amount + 1 }
: { ...item };
});
setCart(newCart);
};
const decreaseAmount = (id, amount) => {
if (amount === 1) {
removeItem(id);
return;
} else {
const newCart = [...cart].map(item => {
return item.id === id
? { ...item, amount: item.amount - 1 }
: { ...item };
});
setCart(newCart);
}
};
const addToCart = book => {
const { id, image, by, bookName,RegularPrice } = book;
const item = [...cart].find(item => item.id === id);
if (item) {
increaseAmount(id);
return;
} else {
const newItem = { id, image, by, bookName, RegularPrice, amount: 1 };
const newCart = [...cart, newItem];
setCart(newCart);
}
};
const clearCart = () => {
setCart([]);
};
return (
<CartContext.Provider
value={{
cart,
cartItems,
total,
removeItem,
increaseAmount,
decreaseAmount,
addToCart,
clearCart
}}
>
{children}
</CartContext.Provider>
);
}
export { CartContext, CartProvider };
从“React”导入React;
函数getCartFromLocalStorage(){
返回localStorage.getItem(“购物车”)
?JSON.parse(localStorage.getItem(“购物车”))
: [];
}
const CartContext=React.createContext();
函数提供程序({children}){
const[cart,setCart]=React.useState(getCartFromLocalStorage());
const[total,setTotal]=React.useState(0);
常量[cartItems,setCartItems]=React.useState(0);
React.useffect(()=>{
setItem(“cart”,JSON.stringify(cart));
让newTotal=cart.reduce((总计,cartItem)=>{
退货(合计+=cartItem.amount*cartItem.price);
}, 0);
newTotal=parseFloat(newTotal.toFixed(2));
setTotal(新总数);
//购物车项目
让newCartItems=cart.reduce((总计,cartItem)=>{
退货(合计+=cartItem.金额);
}, 0);
setCartItems(newCartItems);
},[cart]);
//全局函数
const removietem=id=>{
setCart([…cart].filter(item=>item.id!==id));
};
const increaseAmount=id=>{
const newCart=[…cart].map(项=>{
return item.id==id
?{…项目,金额:项目金额+1}
:{……项目};
});
setCart(newCart);
};
常数递减金额=(id,金额)=>{
如果(金额==1){
removeItem(id);
返回;
}否则{
const newCart=[…cart].map(项=>{
return item.id==id
?{…项,金额:项.金额-1}
:{……项目};
});
setCart(newCart);
}
};
const addToCart=book=>{
const{id,image,by,bookName,RegularPrice}=book;
const item=[…购物车].find(item=>item.id==id);
如果(项目){
增加金额(id);
返回;
}否则{
const newItem={id,image,by,bookName,RegularPrice,amount:1};
const newCart=[…cart,newItem];
setCart(newCart);
}
};
常量clearCart=()=>{
setCart([]);
};
返回(
{儿童}
);
}
导出{CartContext,CartProvider};
购物车项目
import React, { useContext } from "react";
import {Link, useHistory } from 'react-router-dom'
import { CartContext } from "../../context/cart";
import { FaAngleDown, FaAngleUp } from "react-icons/fa";
import Checkout from "./Checkout";
export default function CartItem({ id, image,bookName, RegularPrice, by, amount }) {
const { removeItem, increaseAmount, decreaseAmount } = React.useContext(
CartContext
);
return (
<div id={id} className="cart__item">
<img className='cart__image' src={image} />
<div className='cart__itemdesc'>
<h4>{bookName}</h4>
<h6 className='cart__by'>By: {by}</h6>
<button
className="cart__removebtn"
onClick={() => {
removeItem(id);
}}
>
Remove
</button>
<div>
<button
className="cart-btn amount-btn"
onClick={() => {
increaseAmount(id);
}}
>
<FaAngleUp />
</button>
<p className="item-amount">{amount}</p>
<button
className="cart-btn amount-btn"
onClick={() => {
decreaseAmount(id, amount);
}}
>
<FaAngleDown />
</button>
</div>
</div>
<span className='circle'><span className='circleone'></span></span>
<span className='cart__regular'>{RegularPrice}</span>
<div>
<Checkout />
</div>
</div>
);
}
import React,{useContext}来自“React”;
从“react router dom”导入{Link,useHistory}
从“./../context/cart”导入{CartContext}”;
从“react icons/fa”导入{FaAngleDown,FaAngleUp};
从“/Checkout”导入签出;
导出默认函数CartItem({id,image,bookName,RegularPrice,by,amount}){
const{removietem,increaseAmount,decreateAmount}=React.useContext(
CartContext
);
返回(
{bookName}
作者:{By}
{
removeItem(id);
}}
>
去除
{
增加金额(id);
}}
>
{amount}
{
减少金额(id、金额);
}}
>
{正规价格}
);
}
结帐
import React,{useContext} from 'react'
import { CartContext } from '../../context/cart'
import {Link, useHistory } from 'react-router-dom'
import EmptyCart from './EmptyCart';
const Checkout = () => {
const history = useHistory()
const {cart, total} = useContext(CartContext)
if (cart.length === 0) {
return <EmptyCart />;
}
return (
<div className='checkout'>
<h2>Summary</h2>
<h2>Subtotal : ${total}</h2>
<Link to='/stripecontainer' className='checkout__btnOne'>Proceed to Checkout</Link>
</div>
)
}
export default Checkout
import React,{useContext}来自“React”
从“../../context/cart”导入{CartContext}
从“react router dom”导入{Link,useHistory}
从“/EmptyCart”导入EmptyCart;
常量签出=()=>{
const history=useHistory()
const{cart,total}=useContext(CartContext)
如果(cart.length==0){
返回;
}
返回(
总结
小计:${total}
继续结帐
)
}
导出默认签出
您正在处理坏数据。在这种情况下,正确的响应是向负责后端的人请求经过净化的数据。如果后端的负责人仍然是您,您应该在后端而不是前端解决此问题
长话短说,不要使用parseFloat()
。当您必须将字符串转换为数字时,更安全的方法是使用Number(val)
(或其缩写:+val
)。(不过,这仍然是一个赌注……)
另一件小事:您正在向购物车添加金额为0的物品。它不应该是1
setCart(
cart.concat({
amount: 1,
price: +book.RegularPrice,
...book
})
);
最后一点注意:如果book
已经设置了这些属性,那么您现在拥有的将覆盖对amount
和price
的分配。如果希望对指定具有完全控制(和信心),应首先展开对象,然后指定:
setCart(
cart.concat({
...book,
amount: 1,
price: +book.RegularPrice
})
);
看看。这回答了你的问题吗?似乎在沙箱中工作?请不要继续反复发布相同的问题。如果您有新信息,请编辑原始问题。我不知道它在您的沙盒中如何工作,当在我的沙盒中显示NaNMy sandbox时,我的沙盒正在工作,但我必须在一个项目上单击两次才能算作金额1。