javascript - typescript (类型 'undefined' 不可分配给类型)为什么我的数组有一个 |不明确的？

Question

我有一个名为 combinedMarkets 的数组，它是 5 个或 3 个不同市场数组的组合。所有这些数组都有以下接口(interface) IMarketAsset[]:

export interface IMarketAsset {
  exchange: string;
  base: string;
  quote: string;
  price_quote: string;
  timestamp: string;
}

这是 typescript 错误发生的地方:

const combinedMarkets = asset !== 'BTC' && asset !== 'ETH' ?
  btcMarkets.concat(ethMarkets).concat(marketUSD).concat(marketUSDC).concat(marketUSDT) :
  marketUSD.concat(marketUSDC).concat(marketUSDT);

const filteredMarkets = combinedMarkets.length > 0 ? filterByUSDbase(asset, combinedMarkets) : [];

Argument of type '({ price_quote: string; exchange: string; base: string; quote: string; timestamp: string; } | undefined)[]' is not assignable to parameter of type 'IMarketAsset[]'. Type '{ price_quote: string; exchange: string; base: string; quote: string; timestamp: string; } | undefined' is not assignable to type 'IMarketAsset'. Type 'undefined' is not assignable to type 'IMarketAsset'.ts(2345)

const combinedMarkets: ({
  price_quote: string;
  exchange: string;
  base: string;
  quote: string;
  timestamp: string;
} | undefined)[]

为什么 combinedMarkets 是 IMarketAsset 类型对象或 undefined object 的数组？

完整的 combineExchangeData 函数

// Filter by BTC, ETH, USD, USDT or USDC prices
// If asset has BTC/ETH pairing, obtain exchange BTC/ETH price to calculate assets USD/USDT value
export const combineExchangeData =
  (asset: string, { marketBTC, marketETH, marketUSD, marketUSDT, marketUSDC }: IGetMarketsRes) => {
    const btcBasedExchanges = marketBTC.filter((market: IMarketAsset) => market.base === asset);
    const ethBasedExchanges = marketETH.filter((market: IMarketAsset) => market.base === asset);
    const btcUSDTprices = marketUSDT.filter((market: IMarketAsset) => market.base === 'BTC');
    const btcUSDprices = marketUSD.filter((market: IMarketAsset) => market.base === 'BTC');
    const ethUSDTprices = marketUSDT.filter((market: IMarketAsset) => market.base === 'ETH');
    const ethUSDprices = marketUSD.filter((market: IMarketAsset) => market.base === 'ETH');

    const btcPricedMarkets = filterByExchangeBase(btcBasedExchanges, btcUSDTprices, btcUSDprices);
    const ethPricedMarkets = filterByExchangeBase(ethBasedExchanges, ethUSDTprices, ethUSDprices);

    const btcMarkets = btcPricedMarkets.filter((market) => R.not(R.isNil(market)));
    const ethMarkets = ethPricedMarkets.filter((market) => R.not(R.isNil(market)));

    const combinedMarkets = asset !== 'BTC' && asset !== 'ETH' ?
      btcMarkets.concat(ethMarkets).concat(marketUSD).concat(marketUSDC).concat(marketUSDT) :
      marketUSD.concat(marketUSDC).concat(marketUSDT);

    console.log('combinedMarkets', combinedMarkets);
    const filteredMarkets = combinedMarkets.length > 0 ? filterByUSDbase(asset, combinedMarkets) : [];
    console.log('filteredMarkets', filteredMarkets);

    if (R.isEmpty(filteredMarkets)) return [];

    return filteredMarkets.map((market: IMarketAsset) => {
      if (market) {
        return {
          ...market,
          price_quote: formatPrice(market.price_quote)
        }
      }
    });
  };

实用函数

这是我在主函数中使用的另外 2 个实用函数。此外，我已将问题缩小到 btcMarkets 和 ethMarkets 数组。所以看看 filterByExchangeBase。

import * as R from 'ramda'

import { USD_CURRENCIES } from '../shared/constants/api'
import { IMarketAsset } from '../shared/types'

const calculateBasePrice = (assetBtcPrice: string | number, btcPrice: string | number) => 
  (Number(assetBtcPrice) * Number(btcPrice)).toString();

export const filterByExchangeBase =
  (exchanges: IMarketAsset[], usdtExchanges: IMarketAsset[], usdExchanges: IMarketAsset[]) =>
    exchanges.map((exchange) => {
      let basePriced = usdtExchanges.filter((btcExchange) => btcExchange.exchange === exchange.exchange)[0];

      if (!basePriced) {
        basePriced = usdExchanges.filter((btcExchange) => btcExchange.exchange === exchange.exchange)[0];
      }

      if (basePriced) {
        const { price_quote: assetBtcPrice } = exchange;
        const { price_quote: btcPrice } = basePriced;

        return {
          ...exchange,
          price_quote: calculateBasePrice(assetBtcPrice, btcPrice)
        }
      }
    });

export const filterByUSDbase = (asset: string, combinedMarkets: IMarketAsset[] | undefined) => {
  if (!combinedMarkets) return [];
  return R.not(R.any(R.equals(asset))(USD_CURRENCIES))
    ? combinedMarkets.filter((marketAsset: IMarketAsset) => {
      if (marketAsset && marketAsset.base) {
        return marketAsset.base === asset;
      }
    }) : [];
}

Answer 1

Why is combinedMarkets an array either and object of type IMarketAsset or undefined

因为任何 marketXXX 数组，都是 IMarketAsset | 的数组未定义(而不仅仅是 IMarketAsset。