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JavaScript Asynchronous Code in Express Asynchronous Code in Express Using Callbacks

Posted by babyoscar
babyoscar
12,930 Points

I can't start the server

When I run npm start, it returns a bunch of errors, even though I've tried all the suggestions in the other question about this. How can I fix this? app.js

const express = require('express');
const fs = require('fs');
const path = require('path');

const app = express();

app.set('view engine', 'pug');
app.set("views", path.join(__dirname, "views"));
app.use(express.static('public'));

//CALL BACKS
function getUsers(cb){
  fs.readFile('data.json', 'utf8', (err, data) => {
    if (err) return cb(err);
    const users = JSON.parse(data);
    return cb(null, users);
  });
}

app.get('/', (req,res) => {
  getUsers((err, users) => {
    if (err) {
      res.render('error', {error: err});
    } else {
      res.render('index', {title: "Users", users: users.users})
    }
  });
}); 


app.listen(3000, () => console.log('App listening on port 3000!'));

package.json:

{
  "name": "async-express",
  "version": "1.0.0",
  "description": "",
  "main": "app.js",
  "scripts": {
    "start": "nodemon"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "express": "^4.16.4",
    "pug": "^2.0.3"
  },
  "devDependencies": {
    "nodemon": "^1.18.9"
  }
}

Can someone help? Thanks.

Ashish Mehra
Ashish Mehra
2,411 Points

Hi babyoscar,

Will you please share the error logs.

Thanks,

babyoscar
babyoscar
12,930 Points

Sure, it says

npm ERR! code ENOENT
npm ERR! syscall open
npm ERR! path C:\Users\babyoscar\package.json
npm ERR! errno -4058
npm ERR! enoent ENOENT: no such file or directory, open 'C:\Users\babyoscar\package.json'
npm ERR! enoent This is related to npm not being able to find a file.   
npm ERR! enoent

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\babyoscar\AppData\Roaming\npm-cache\_logs\2020-12-19T19_00_49_433Z-debug.log
Ashish Mehra
Ashish Mehra
2,411 Points

From above log what I'm able to figure out is you're running command "npm start" in wrong path.

As log says 

 no such file or directory, open 'C:\Users\babyoscar\package.json'

Make sure you're running the command in right place and have all the dependencies install before doing npm start.

babyoscar
babyoscar
12,930 Points

Hmm, I ran npm install last time, and I'm doing it in the app.js file. Am I supposed to do something else?

3 Answers

Nghia Nguyen
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
Nghia Nguyen
Front End Web Development Techdegree Graduate 15,522 Points
Nghia Nguyen
.a{fill-rule:evenodd;}techdegree seal-36
Nghia Nguyen
Front End Web Development Techdegree Graduate 15,522 Points

in your start script can you try "npx nodemon" instead?

babyoscar
babyoscar
12,930 Points

Thanks! It worked.

Ashish Mehra
Ashish Mehra
2,411 Points
Ashish Mehra
Ashish Mehra
2,411 Points

Let say project structure is something like this 

 project
    -app.js
    -package.json

For something like this 

 project
   src
     -app.js
   package.json

In above both cases you need to run npm commands inside of project directory because it should be run from path where your package.json exist not app.js.

babyoscar
babyoscar
12,930 Points

Well, I ran it in the V2_starter_files_callbacks folder's app.js, and the package.json file is inside the same folder, but should I run it from package.json then?

Ashish Mehra
Ashish Mehra
2,411 Points

As per the log you're running command in 

C:\Users\babyoscar\

It should be in project directory. Can you confirm the path?

babyoscar
babyoscar
12,930 Points

Oh, I think I get it. I have to run cd directoryName before that right?

babyoscar
babyoscar
12,930 Points

Okay, now it throws a different error, it says:

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! async-express@1.0.0 start: `nodemon`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the async-express@1.0.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm WARN Local package.json exists, but node_modules missing, did you mean to install?

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\babyoscar\AppData\Roaming\npm-cache\_logs\2020-12-20T21_14_16_744Z-debug.log
Ashish Mehra
Ashish Mehra
2,411 Points
Ashish Mehra
Ashish Mehra
2,411 Points

Have you installed all dependencies. If yes, than follow Nghia Nguyen comment.

babyoscar
babyoscar
12,930 Points

Okay, thanks.