app post is not working i am not getting the output - node.js

Question

var express = require("express");
var app = express();
var bodyParser = require('body-parser');
var port = 3000;
const fs = require('fs');
// we are connecting to the mangodb using mangoose
var mongoose = require("mongoose");
// Now we are using bodyParser
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
mongoose.connect("mongodb://localhost:27017/YourDB", { useNewUrlParser: true })
// now we are creating the schema to the database
var nameSchema = new mongoose.Schema({
firstName: String,
lastNameName: String
});
// Now we have to create a model
var User = mongoose.model("User", nameSchema);
app.use("/", (req, res) => {
res.sendFile(__dirname + "/index.html");
});
// Now we are posting the data
app.post("/addname", (req, res) => {
console.log("nnnnnn")
console.log(req.body.firstName)
var myData = new User(req.body);
myData.save()
console.log(myData);
fs.writeFile(__dirname +"/data.json",myData, function(err){
if(err) {
return console.log(err);
}
console.log("The file is saved ");
})
console.log(myData)
})
// Now we are getting the data
app.listen(port, () => {
console.log("Server listening on port " + port);
});
1)I am using express app.post to post the data into database and store the data into the write file to check
2) app.post is not working it tried console.log to check but it is not going inside the function
3) I am not getting output as well as any error plese help me

Answer 1

there is no error handling and response handling in this code.
it will be readable if we write post method with async/await :
app.post("/addname", async (req, res) => {
console.log("nnnnnn")
console.log(req.body.firstName)
var myData = new User(req.body);
await myData.save()
console.log(myData);
fs.writeFileSync(__dirname +"/data.json", myData)
console.log(myData)
})

Answer 2

you will add next() to app.use
var User = mongoose.model("User", nameSchema);
app.use("/", (req, res,next) => {
res.sendFile(__dirname + "/index.html");
next()
});
// Now we are posting the data
app.post("/addname", (req, res) => {
console.log("nnnnnn")
console.log(req.body.firstName)
var myData = new User(req.body);
myData.save()
console.log(myData);
fs.writeFile(__dirname +"/data.json",myData, function(err){
if(err) {
return console.log(err);
}
console.log("The file is saved ");
})
console.log(myData)
})
// Now we are getting the data
app.listen(port, () => {
console.log("Server listening on port " + port);
});

Answer 3

That's because every request is going to this app.use code block. app.use("/", (req, res) => { ... });
Just Put it below the app.post("/addname", (req, res) => { ... });
app.use is used to mount middlewares into the request-response chain. So, every request that comes matches the /(which is essentially every request) goes inside that middleware. So, use your routes first then use the middleware at the end.
EDIT:
Let me give you a mcve which I tested locally:
const express = require('express');
const fakeData = function(){
return {
s: "fakeData"
}
}
const app = express();
const port = 8181
const path = require('path')
app.get("/a", (req, res) => {
return res.json({d:'yay'});
});
app.use('/',(req,res)=>{
return res.json(fakeData());
})
app.listen(port, () => {
console.log(`Server started on PORT ${port}`);
});
Because every request goes through a mounted middleware, so when you GET/POST/ANYTHING to localhost:8181/<abosulutely_any_path> it will go through the app.use because it treats that function as middleware and will return { s: "fakeData" }.
But when you make a GET call http://localhost:8181/a it will go to the app.get route BECAUSE WE DECLARED IT FIRST and return { d : "yay" }