为什么我的 boolean 语句总是评估为真？

Question

我对 javascript 很陌生，我正在尝试弄清楚如何根据美国各州计算销售税。 在我的代码中，我尝试使用基于 state 输入值的 if else 语句来完成此操作。 但是，无论我为 state 的价值投入多少，税收都是根据 8.75% 确定的，我不确定我做错了什么。 我非常感谢有关如何解决此问题的任何帮助或建议。

谢谢

PlaceOrderScreen.js

import React, { useEffect } from 'react';
import { useDispatch, useSelector } from 'react-redux';
import { Link } from 'react-router-dom';
import { createOrder } from '../actions/orderActions';
import CheckoutSteps from '../components/CheckoutSteps';
import { ORDER_CREATE_RESET } from '../constants/orderConstants';
import LoadingBox from '../components/LoadingBox';
import MessageBox from '../components/MessageBox';

export default function PlaceOrderScreen(props) {
  const cart = useSelector((state) => state.cart);
  if (!cart.paymentMethod) {
    props.history.push('/payment');
  }
  const orderCreate = useSelector((state) => state.orderCreate);
  const { loading, success, error, order } = orderCreate;
  const toPrice = (num) => Number(num.toFixed(2)); // 5.123 => "5.12" => 5.12
  cart.itemsPrice = toPrice(
    cart.cartItems.reduce((a, c) => a + c.qty * c.price, 0)
  );
//Sales Tax//
   {
  if (cart.shippingAddress.state === 'New York'||'NY'){
  cart.taxPrice = toPrice(0.0875 * cart.itemsPrice)}
  else if (cart.shippingAddress.state === 'Kansas'||'KS') {
   cart.taxPrice = toPrice(0.065 * cart.itemsPrice)}
  else {
    cart.taxPrice = toPrice(0 * cart.itemsPrice)}
  };
  cart.totalPrice = cart.itemsPrice + cart.shippingPrice + cart.taxPrice;
  const dispatch = useDispatch();
  const placeOrderHandler = () => {
    dispatch(createOrder({ ...cart, orderItems: cart.cartItems }));
  };
  useEffect(() => {
    if (success) {
      props.history.push(`/order/${order._id}`);
      dispatch({ type: ORDER_CREATE_RESET });
    }
  }, [dispatch, order, props.history, success]);
  return (
    <div>
      <CheckoutSteps step1 step2 step3 step4></CheckoutSteps>
      <div className="row top">
        <div className="col-2">
          <ul>
            <li>
              <div className="card card-body">
                <h2>Shipping</h2>
                <p>
                  <strong>Name:</strong> {cart.shippingAddress.fullName} <br />
                  <strong>Address: </strong> {cart.shippingAddress.address},
                  {cart.shippingAddress.city}, {cart.shippingAddress.state}, {cart.shippingAddress.postalCode}
                  ,{cart.shippingAddress.country}
                </p>
              </div>
            </li>
          </ul>
        </div>
      </div>
    </div>

ShippingAddressScreen.js

import React, { useState } from 'react';
import { useDispatch, useSelector } from 'react-redux';
import { saveShippingAddress } from '../actions/cartActions';
import CheckoutSteps from '../components/CheckoutSteps';

export default function ShippingAddressScreen(props) {
  const userSignin = useSelector((state) => state.userSignin);
  const { userInfo } = userSignin;
  const cart = useSelector((state) => state.cart);
  const { shippingAddress } = cart;
  if (!userInfo) {
    props.history.push('/signin');
  }
  const [fullName, setFullName] = useState(shippingAddress.fullName);
  const [address, setAddress] = useState(shippingAddress.address);
  const [city, setCity] = useState(shippingAddress.city);
  const [state, setState] = useState(shippingAddress.state);
  const [postalCode, setPostalCode] = useState(shippingAddress.postalCode);
  const [country, setCountry] = useState(shippingAddress.country);
  const dispatch = useDispatch();
  const submitHandler = (e) => {
    e.preventDefault();
    dispatch(
      saveShippingAddress({ fullName, address, city, state, postalCode, country })
    );
    props.history.push('/payment');
  };
  return (
    <div>
      <CheckoutSteps step1 step2></CheckoutSteps>
      <form className="form" onSubmit={submitHandler}>
        <div>
          <h1>Shipping Address</h1>
        </div>
        <div>
          <label htmlFor="fullName">Full Name</label>
          <input
            type="text"
            id="fullName"
            placeholder="Enter full name"
            value={fullName}
            onChange={(e) => setFullName(e.target.value)}
            required
          ></input>
        </div>
        <div>
          <label htmlFor="address">Address</label>
          <input
            type="text"
            id="address"
            placeholder="Enter address"
            value={address}
            onChange={(e) => setAddress(e.target.value)}
            required
          ></input>
        </div>
        <div>
          <label htmlFor="city">City</label>
          <input
            type="text"
            id="city"
            placeholder="Enter city"
            value={city}
            onChange={(e) => setCity(e.target.value)}
            required
          ></input>
        </div>
        <div>
          <label htmlFor="state">State</label>
          <input
            type="text"
            id="state"
            placeholder="Enter state"
            value={state}
            onChange={(e) => setState(e.target.value)}
            required
          ></input>
        </div>
        <div>
          <label htmlFor="postalCode">Postal Code</label>
          <input
            type="text"
            id="postalCode"
            placeholder="Enter postal code"
            value={postalCode}
            onChange={(e) => setPostalCode(e.target.value)}
            required
          ></input>
        </div>
        <div>
          <label htmlFor="country">Country</label>
          <input
            type="text"
            id="country"
            placeholder="Enter country"
            value={country}
            onChange={(e) => setCountry(e.target.value)}
            required
          ></input>
        </div>
        <div>
          <label />
          <button className="primary" type="submit">
            Continue
          </button>
        </div>
      </form>
    </div>
  );
}

Answer 1

您的代码应如下所示：

cart.shippingAddress.state === 'New York'|| cart.shippingAddress.state === 'NY'

您当前的代码正在测试字符串“NY”是否为真，并且在您的 boolean 测试中评估为真，因此您始终获得 8.75% 的税率。