javascript - Node.js - TypeError : res. json 不是函数(在某些路由中工作，在其他路由中不起作用)

Question

在 MERN 堆栈(Mongo、Express、React、Node)中工作并在我的 API 中遇到错误。

这是我的 plaid.js 文件，其中我的路线之一引发了此错误。当然，我已经删除了所有 secret token 变量，但假设一切正常，直到出现 res.json 错误(确实如此)。

        const express = require("express");
        const plaid = require("plaid");
        const router = express.Router();
        const jwt = require("jsonwebtoken");
        const keys = require("../../config/keys");
        const passport = require("passport");
        const moment = require("moment");
        const mongoose = require("mongoose");

        // Load Account and User models
        const Account = require("../../models/Account");
        const User = require("../../models/User");

        // Replaced my actual keys with empty strings for sake of this post
        const PLAID_CLIENT_ID = "";
        const PLAID_SECRET = "";
        const PLAID_PUBLIC_KEY = "";

        const client = new plaid.Client(
          PLAID_CLIENT_ID,
          PLAID_SECRET,
          PLAID_PUBLIC_KEY,
          plaid.environments.sandbox,
          { version: "2018-05-22" }
        );

        var PUBLIC_TOKEN = null;
        var ACCESS_TOKEN = null;
        var ITEM_ID = null;

        // @route POST api/plaid/accounts/add
        // @desc Trades public token for access token and stores credentials in database
        // @access Private
        router.post(
          "/accounts/add",
          passport.authenticate("jwt", { session: false }),
          (req, res) => {
            PUBLIC_TOKEN = req.body.public_token;

            const userId = req.user.id;
            const institution = req.body.metadata.institution;
            const { name, institution_id } = institution;

            if (PUBLIC_TOKEN) {
              client
                .exchangePublicToken(PUBLIC_TOKEN)
                .then(res => {
                  ACCESS_TOKEN = res.access_token;
                  ITEM_ID = res.item_id;

                  // Check if account already exists for specific user
                  Account.findOne({
                    userId: req.user.id,
                    institutionId: institution_id
                  })
                    .then(account => {
                      if (account) {
                        console.log("Account already exists");
                      } else {
                        const newAccount = new Account({
                          userId: userId,
                          publicToken: PUBLIC_TOKEN,
                          accessToken: ACCESS_TOKEN,
                          itemId: ITEM_ID,
                          institutionId: institution_id,
                          institutionName: name
                        });

                        // TO:DO fix error, res.json is not a function
                        newAccount.save().then(account => res.json(account));
                      }
                    })
                    .catch(err => console.log(err)); // Mongo Error
                })
                .catch(err => console.log(err)); // Plaid Error
            }
          }
        );
    module.exports = router;

newAccount.save() 执行得很好，但后续的 res.json 会抛出错误。这是我返回的错误。也就是说，res.json 不是一个函数。

[0] (node:23413) UnhandledPromiseRejectionWarning: TypeError: res.json is not a function
[0]     at newAccount.save.then.account (/Users/rishi/plaid-auth/routes/api/plaid.js:97:55)
[0]     at process._tickCallback (internal/process/next_tick.js:68:7)

这里有很多帖子都提到 res.json is not a function 错误，但所提出的解决方案都不适合我。我很困惑为什么会抛出这个错误，因为我在应用程序的另一部分使用相同的约定，并且 res.json 工作得很好。请参阅下面的示例，了解 res.json 的工作原理。

// @route POST api/posts
// @desc Create a post
// @access Private
router.post(
  "/",
  passport.authenticate("jwt", { session: false }),
  (req, res) => {
    const { errors, isValid } = validatePostInput(req.body);

    // Check validation
    if (!isValid) {
      return res.status(400).json(errors);
    }

    const newPost = new Post({
      text: req.body.text,
      name: req.body.name,
      avatar: req.body.avatar,
      user: req.user.id // current logged in user
    });

    // res.json works just fine
    newPost.save().then(post => res.json(post));
  }
);

Answer 1

因为这段代码

if (PUBLIC_TOKEN) {
          client
            .exchangePublicToken(PUBLIC_TOKEN)
            .then(res => {
              ACCESS_TOKEN = res.access_token;

当你执行这一行newAccount.save().then(account => res.json(account));时，res不再是函数router上的那个.post('/accounts/add', (req, res) => {})

因此，解决方案很简单，将 promise exchangePublicToken 中的 res 更改为其他内容，如下例所示。

您将 Promise 回调中的参数命名为与上面 router.post 中的回调中的参数相同

if (PUBLIC_TOKEN) {
          client
            .exchangePublicToken(PUBLIC_TOKEN)
            .then(exchangeResponse => {
              ACCESS_TOKEN = exchangeResponse.access_token;