SyntaxError: Unexpected token b in JSON at position 3 - node.js

Question

i am new to MERN framework
try to use postman to test my get and post request. but keep getting this error SyntaxError: Unexpected token b in JSON at position 3
here is my schema -------------------------
const mongoose = require("mongoose");
const Schema = mongoose.Schema;
const UserSchema = new Schema({
firstname: {
type: String,
required: true
},
lastname: {
type: String,
required: true
},
sex: {
type: String,
required: true
},
age: {
type: Number,
required: true
},
password: {
type: String,
required: true
},
admin: {
type: Boolean,
default: true
}
});
module.exports = User = mongoose.model("user", UserSchema);
here is my route---------------------
const express = require("express");
const router = express.Router();
const User = require("../../models/user");
router.get("/", (req, res) => {
User.find()
.sort({ age: -1 })
.then(users => res.json(users));
});
router.post("/", (req, res) => {
const newUser = new User({
firstname: req.body.firstname
});
newUser.save().then(user => res.json(user));
});
module.exports = router;
here is my server------------------
const express = require("express");
const mongoose = require("mongoose");
const users = require("./routes/api/users");
const app = express();
app.use(express.json());
const db = require("./config/keys").mongoURI;
mongoose
.connect(db, { useNewUrlParser: true, useUnifiedTopology: true })
.then(() => console.log("MongoDB Connected"))
.catch(err => console.log(err));
app.use("/api/users", users);
const port = 5000;
app.listen(port, () => console.log(`server started on port ${port}`));
please help!! stuck for whole day

Answer 1

You do not need express.json() for GET routes. So please try moving app.use(express.json()); to route file before POST request.
Also if you are using express version >= 4, please use app.use(bodyParser.json()) from body-parser package.