node.js - In Node js, why is my controller.js not showing the data after invoking a model.js function

Question

I'm new to Nodejs and i've fetched a json file using require and fs, and using MVC , i have a model.js that has the function that reads the json file, but when the controller invokes the model function, the data is not shown (console.log(data) in the controller, but console.logged in the model.js. Here is my code:

controller.js

exports.renderHomePage = (req, res) => {
    
    apiServerModel.loadTeams()
        .then(function (data) {
            console.log(data);
            console.log("This is inside controller")
            res.render("index", { // output as string
                teamsList: `${JSON.stringify(data, null, 2)}`    // A property called teamList to be displayed on the browser
                //teamsList: teamView.TeamsView(`${JSON.stringify(data, null, 2)}`)
        })
    })
    .catch(error => console.log(error))
}

model.js

'use strict';

const fs = require('fs');

class TeamsModel {

    static async loadTeams() {  
      try {
           await fs.readFile('./json/prov-nodes.json', (err, rawData) => {
          if (err) throw err;
          let teams = JSON.parse(rawData);
          return teams;
          //console.log(teams);
        });
      } catch (error) {
        console.log(error)
      }
      console.log('This is after the read call');
    }

  }

  exports.TeamsModel = TeamsModel; 

question from:https://stackoverflow.com/questions/65649339/in-node-js-why-is-my-controller-js-not-showing-the-data-after-invoking-a-model

Answer 1

first of all you should read about Callbacks VS Promises VS Async/Await in node.js.

when you use async/await, don't have a callback so:

use fs/promises instead of fs, because you used await for fs in your loadTeams function.

'use strict';

const fs = require('fs/promises');

class TeamsModel {

    static async loadTeams() {  
      console.log("hi")
      try {
           let rawData = await fs.readFile('./json/prov-nodes.json')
          let teams = JSON.parse(rawData);
          return teams;

      } catch (error) {
        console.log(error)
      }
      console.log('This is after the read call');
    }

  }

  module.exports = TeamsModel;