我遇到了CORS问题。在我的functions/index.js中，我有：

const cors = require('cors')({
  origin: true
});

我的端点是https://sis-t.redsys.es:25443/sis/realizarPago .我需要做一个POST到这个url与appropriate参数从客户端，这是外部的firebase环境.我也有正确的计划，以允许外部网络，但使请求到一个不同的地址比源之一，触发CORS问题：

• error log
• network log

我读到过你只需要修改头部，但这只适用于你向自己的服务器发出请求的情况。当你执行http.onRequest()时，你可以在函数内部使用中间件，但当你向外部服务器发出POST时会发生什么呢？
以下是执行POST的axios函数：

cardPay: function () {
  this.cardProcess = true
    axios({
      method: 'post',
      url: 'https://us-central1-cutre-windrider.cloudfunctions.net/cardPay',
      data: {
        verifiedUserLogged: this.userLogged.uid,
        cart: this.cartItemList,
        finalPrice: this.serverPrice,
        deliveryInfo: this.userLogged.deliveryAdress,
        name: this.userLogged.displayName || false,
        email: this.userLogged.email
      }
    })
    .then(response => {
      this.requestData = response
      this.redsysRedirect(response.data.data)
    })
    .catch(console.log)
    },
redsysRedirect: function (data) {
  axios.post('https://sis-t.redsys.es:25443/sis/realizarPago', {
    'Ds_SignatureVersion': 'HMAC_SHA256_V1',
    'Ds_MerchantParameters': data.merchantParameters,
    'Ds_Signature': data.signature
  }).then(console.log).catch(console.log)

以下是服务器端函数：

exports.cardPay = functions.https.onRequest((req, res) => {
  return cors(req, res, () => {
    const cart = req.body.cart
    const user = req.body.verifiedUserLogged
    const key = admin.database().ref(`sales/${user}`).push().key
    processCart(cart).then(result => {
      console.info(createPayment(result, key))
      return res.json({ "data": createPayment(result, key) }).end()
    }).catch(console.log)
  })
})

function processCart(cart) {
  return new Promise((resolve, reject) => {
    Promise.all(cart.map(i => switcher(i)))
      .then(prices => resolve(
        prices.reduce(
          (finalPrice, price) => price + finalPrice, 0)
      )).catch(console.log)
  });
}

function switcher(item) {
  switch (item.destiny) {
    case 'bookedLessons':
        return lessonPrice(item.name, item.index)
      case 'bookedRentals':
        return rentalPrice(item.id, item.index, item.insurancePurchased, item.insuranceId)
      case 'bookedLodgins':
        return item.reservationData ? roomPriceWithReservation(item.id, item.quantity, item.persons, item.reservationData) : roomPriceNoReservation(item.id, item.quantity, item.persons)
      case 'deliveries':
        return productPrice(item.id, item.quantity)
      case 'bookedCar':
        return carPrice(item.id, item.index)
      case 'bookedStorage':
        return storagePrice(item.index)
      case 'bookedTransportation':
        return transportationPrice(item.id, item.index, item.persons, item.roundTrip)
      case 'bookedDoublePack':
        return doublePack(item.id, item.persons)
      case 'bookedTriplePack':
        return triplePack(item.id, item.persons)
      default:
        break
  }
}

function createPayment(total, orderId) {
  let redsys = new Redsys();
  let mParams = {
      "DS_MERCHANT_AMOUNT":total.toString(),
      "DS_MERCHANT_ORDER":orderId,
      "DS_MERCHANT_MERCHANTCODE":   "025988262",
      // "DS_MERCHANT_MERCHANTCODE":tpvInfo.fucCode,
      "DS_MERCHANT_CURRENCY":"978",
      // "DS_MERCHANT_CURRENCY":tpvInfo.currency,
      "DS_MERCHANT_TRANSACTIONTYPE":"0",
      // "DS_MERCHANT_TRANSACTIONTYPE":tpvInfo.transaction_type,
      "DS_MERCHANT_TERMINAL":   "001",
      // "DS_MERCHANT_TERMINAL":tpvInfo.terminal,
      "DS_MERCHANT_MERCHANTURL":'http://localhost:8080',
      "DS_MERCHANT_URLOK":'http://localhost:8080/home?foo=true',
      "DS_MERCHANT_URLKO":'http://localhost:8080/home?foo=false'
  };
  return  {signature: redsys.createMerchantSignature(/* tpvInfo.secret */   "sq7HjrUOBfKmC576ILgskD5srU870gJ7", mParams) , merchantParameters: redsys.createMerchantParameters(mParams), raw: mParams};
}