query.on is not a function

Question

I am trying to learn how to use javascript to connect to a postgresql database but when I try to log a query to the console using query.on(...), I get a type error that says "query.on is not a function". I have searched extensively on how to resolve this but can't seem to find any documentation on the .on function. I know that the connection is successful because when I query the db from terminal, the two new rows have been added.

jsontest.js

var pg = require('pg');
var conString = "postgres://[username]:[password]@localhost:5432/VONKTA1";
//username and password masked

var client = new pg.Client(conString);

client.connect();

client.query("INSERT INTO json_test (name, attributes) VALUES ('Ted', $1)", [{"age": 2, "gender": "M"}]);
client.query("INSERT INTO json_test (name, attributes) VALUES ('Sarah', $1)", [{"age": 8, "gender": "F"}]);

console.log("about to query");

var query = client.query("SELECT * FROM json_test");

query.on('row', function(row) {
    console.log(row);
});

query.on('end', function() {
    client.end();
});

package.json

{
  "name": "test",
  "version": "1.0.0",
  "description": "",
  "main": "test.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "pg": "^7.0.2",
  }
}

Answer 1

query.on has been removed from node-pg 7.

See https://node-postgres.com/guides/upgrading for how to properly handle rows.

The usual way is to use promises or async/await (using promises in a clearer way):

await client.connect();
var res = await client.query("SELECT * FROM json_test");
res.rows.forEach(row=>{
    console.log(row);
});
await client.end();

Answer 2

this is how it works for me :

var pg = require("pg");

var connectionString = {
  user: 'user',
  host: 'host',
  database: 'db',
  password: 'pass',
  port: 5432,
};

var pool = new pg.Pool(connectionString);

pool.connect(function(err, client, done) {

    const query = client.query(new pg.Query("SELECT * from products"))
    query.on('row', (row) => {
        console.log(row);
    })
    query.on('end', (res) => {
        // pool shutdown
        console.log("ending");
        pool.end()
    })
    query.on('error', (res) => {
        console.log(res);
    })

    done()
})

source : https://node-postgres.com/features/connecting

Answer 3

As Mentioned by Denys Séguret in Answer, the function query.on is deprecated. And if you are a beginner and want to get a quick connection to try out your queries without being bothered by async/await functionality. You can try the below code:-

const { Pool, Client } = require('pg')
const connectionString = 'postgresql://dbuser:dbpassword@database.server.com:5432/mydb'

const pool = new Pool({
  connectionString: connectionString,
})

pool.query('SELECT NOW()', (err, res) => {
  console.log(err, res)
  pool.end()
})