I don't know what have bellow error: TypeError: res.json is not a function

I readed express documentation, and don't see any wrong syntax or other errrors.

Code:

• index.js

import express from "express";
import postRoutes from "./routes/posts.js";

const app = express();

app.use(express.json());
app.use("/api/posts", postRoutes);

app.listen(8800, () => {
  console.log("Server is running on port 8800");
});

• ./routes/posts.js

import express from "express";

const router = express.Router();

router.get("/", (res, req) => {
  res.json("This works!");
});

export default router;

CodePudding user response：

Because the request object indeed has no json() function.

You mixed up the parameter names and called the request object res and the response object req. Swap them to make it less confusing:

router.get("/", (req, res) => {
  res.json("This works!");
});

CodePudding user response：

edit:

router.get("/", (res, req) => {
  res.json("This works!");
});

to

router.get("/", (req, res) => {
  res.json("This works!");
});

the (res, req) has to be in a specific order

CodePudding user response：

The arguments in router.get are wrong. Its (req, res) now (res, req)

This is how it should look like:

router.get("/", (req, res) => {
  res.json("This works!");
});

CodePudding user response：

The first argument to the Handler is always request and the second is response often written in short from req and res. So change your code to this. More on this in this routing documentation

router.get("/", (req, res) => {
  res.json("This works!");
});

Note: Your code will also work if you change your res.json() to req.json() since you have switched the conventional names. But doing this is confusing and I will not recommend doing it.