Create and initialize your a directory for your Express application.
$ mkdir node-knex-demo
$ cd node-knex-demo
$ npm initKnex is a SQL query builder, mainly used for Node.js applications with built in model schema creation, table migrations, connection pooling and seeding.
Install knex globally on your local computer.
$ npm install knex -gThis will allow us to use knex as a command line tool that helps you create and manage your knex files.
In addition, you will need to also install the knex module locally to use in your project.
$ npm install knex --saveFor our example, we're going to be connecting to a PostgreSQL database, we'll need to install the pg module.
$ npm install pg --save
We can start by creating a knexfile.js in the root of your project which will act as our configuration for different environments, (e.g. – local development vs production).
$ knex init
This will create a knexfile.js with the different configurations for the different environments.
Generated output knexfile.js.
module.exports = {
development: {
client: 'sqlite3',
connection: {
filename: './dev.sqlite3'
}
},
staging: {
client: 'postgresql',
connection: {
database: 'my_db',
user: 'username',
password: 'password'
},
pool: {
min: 2,
max: 10
},
migrations: {
tableName: 'knex_migrations'
}
},
production: {
client: 'postgresql',
connection: {
database: 'my_db',
user: 'username',
password: 'password'
},
pool: {
min: 2,
max: 10
},
migrations: {
tableName: 'knex_migrations'
}
}
};Edit your development settings in knexfile.js to point to your postgres database, using your db username and password. DON'T FORGET TO CREATE YOUR DATABASE LOCALLY!
Example development config object
{
development: {
client: 'pg',
connection: {
host : '127.0.0.1',
user : '[db_username]',
password : '[db_password]',
database : '[db_name]',
charset: 'utf8'
},
migrations: {
directory: __dirname + '/knex/migrations',
},
seeds: {
directory: __dirname + '/knex/seeds'
}
}
}We want to create a knex directory at the root of our project to hold our migrations and seeds scripts. Inside of the knex directory, we need a knex.js file to hold the single instance of the knex module with the correct environment config.
$ mkdir knex
$ mkdir knex/migrations
$ mkdir knex/seeds
$ touch knex/knex.jsAt this point, our project structure should look like this:
.
├── knex
│ └── migrations
│ └── seeds
│ └── knex.js
└── knexfile.js
└── package.json
For more information on migrations and seeds with knex, checkout the knex migrations and seeds guide.
Example knex.js
const environment = process.env.ENVIRONMENT || 'development'
const config = require('../knexfile.js')[environment];
module.exports = require('knex')(config);$ npm install express --save
Now let's create a server.js file in the root of your project. Create your express application how you normally would, for this example the server listening on port 3001. Let's also create a super basic GET endpoint to query our db.
const express = require('express');
const PORT = process.env.PORT || 3001;
const knex = require('./knex/knex.js');
const app = express();
app.get('/tasks', (req, res) => {
// use the knex variable above to create dynamic queries
});
app.listen(PORT, () => {
console.log(`Listening on port: ${PORT}`);
});Start the server:
$ node server.js
Hello! Great guide.
I couldn't really follow this part though: how do I send the ENVIRONMENT variable to knex to decide which connection to pick from the knexfile?
Right now I have a connection.js file that looks like this (using ES6):
I'm sorry, I think this sounds like an obvious question, I'm just not familiar with the syntax presented in
const config = require('../knexfile.js')[environment];, passing the variable through brackets.