'pg' package TypeError: Cannot read properties of undefined (reading 'then')

Question

When I try to run then function on it, it will return this error

TypeError: Cannot read properties of undefined (reading 'then')
at Object.\<anonymous\> (/app/src/index.js:52:2)
at Module.\_compile (node:internal/modules/cjs/loader:1546:14)
at Module.\_extensions..js (node:internal/modules/cjs/loader:1691:10)
at Module.load (node:internal/modules/cjs/loader:1317:32)
at Module.\_load (node:internal/modules/cjs/loader:1127:12)
^

const { Client } = require('pg');

const PG_USER = 'root';
const PG_PASSWORD = 'example';
const PG_HOST = 'postgres';
const PG_PORT = '5432';
const PG_URI = `postgresql://${PG_USER}:${PG_PASSWORD}@${PG_HOST}:${PG_PORT}`;

const client =  new Client({
  connectionString: PG_URI,
});

client.connect(PG_URI)
  .then( () =>console.log('connect to postgresdb...'))
  .catch((err)=>console.log('failed connect to postgresdb:' ,err))

version: 10.8.1

mohamed moniem
– mohamed moniem

2024-08-24 07:44:54 +00:00
Commented Aug 24, 2024 at 7:44 — mohamed moniem
– mohamed moniem, Commented Aug 24, 2024 at 7:44
"pg": "^8.12.0"

mohamed moniem
– mohamed moniem

2024-08-24 08:46:21 +00:00
Commented Aug 24, 2024 at 8:46 — mohamed moniem
– mohamed moniem, Commented Aug 24, 2024 at 8:46

mhborthwick · Accepted Answer · 2024-08-25 05:31:48Z

2

I think you need to remove PG_URI from your client.connect method call. You've already provided PG_URI when you instantiated Client. As far as I can tell, client.connect doesn't take any arguments and is used just to initiate the connection to your database.

Edit: Per the comment below, you can pass a callback but then it doesn’t return a promise.

edited Aug 25, 2024 at 5:31

answered Aug 24, 2024 at 8:57

mhborthwick

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6 Comments

Jaromanda X Over a year ago

pg.connect can take an argument ... a callback ... and if an argument is supplied, it doesn't return a Promise - which explains the error perfectly, since presumably it returns undefined when an argument is present, and undefined famously has no .then method

mohamed moniem Over a year ago

@mhborthwick if i remove PG-URI from client.connect call , it change the error to failed connect to postgresdb: Error: connect EHOSTUNREACH 172.18.0.2:5432 at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1605:16) { errno: -113, code: 'EHOSTUNREACH', syscall: 'connect', address: '172.18.0.2', port: 5432 }

mohamed moniem Over a year ago

@Jaromanda , so what should i do ?

Jaromanda X Over a year ago

@mohamedmoniem EXACTLY what this answer tells you to do ¯\_(ツ)_/¯

mhborthwick Over a year ago

Thanks @Jaromanda - edited my answer per your comment.

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