How to use Knex object in other file?

Question

How do I use the knex db object inside other files?

For Example

my index.js

const app = require("express")();
const cors = require("cors");
const bodyParser = require("body-parser");
const user = require("./routes/User");
const product = require("./routes/Product");

//-----------------
const db = require("knex")({
  client: "pg",
  connection: {
    host: "127.0.0.1",
    user: "postgres",
    password: "",
    database: "Razer"
  }
});

//-----------------
app.use(cors());
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));

//-----------------
app.use("/user", user);
app.use("/product", product);

//-----------------
module.exports = db;

//-----------------
app.listen(5000, () => {
  console.log("App listening on PORT 5000 ");
});

my User.js

const express = require("express");
const router = express.Router();
const db = require("../index");

router.get("/", async (req, res) => {
  console.log(db);
});

module.exports = router;

when am trying to use the db object inside User.js it's not working and giving me an empty object

Answer 1

You are having cyclic reference between User.js and index.js. So db has not been created yet when you are requesting it in User.js.

If you really want to keep one globally declared knex instance, you should create separate db.js file, which just creates knex and require it in both index.js and User.js files.

Answer 2

knexfile.js

const path = require('path');
    
    module.exports = {
      development: {
        client: 'mysql',
        connection: {
          host: 'localhost',
          port: 3306,
          user: 'root',
          password: '',
          database: 'e_transport',
        },
        migrations: {
          directory: path.join(__dirname, './src/migrations'),
        },
        useNullAsDefault: true,
      },
    
      production: {
        client: 'mysql',
        connection: {
          host: 'localhost',
          port: 3306,
          user: 'root',
          password: '',
          database: 'e_transport',
        },
        migrations: {
          directory: path.join(__dirname, './src/migrations'),
        },
        useNullAsDefault: true,
      },
    };

Then crate file db.js and write the code inside file :

const config = require('../../knexfile')
const knex = require('knex')(config);

module.exports = knex;

And finally use where are you use

db(table).select(data).then((result) => { console.log('result', result) });