Angular: Can't use 'require' keyword

Question

In my app, i need to use the require keyword to import something. But i can't. It shows the error below:

ERROR in src/app/components/test1/test1.component.ts:3:24 - error TS2591: Cannot find name 'require'. Do you need
to install type definitions for node? Try `npm i @types/node` and then add `node` to the types field in your tsconfig.

3 const {Pool, Client} = require('pg');

test1.component.ts

import { Component, OnInit } from '@angular/core';

const {Pool, Client} = require('pg');
const connectionString = 'postgressql;://postgres:1@localhost:3000/test1';

const client = new Client({connectionString});

client.connect();

client.query('select * from posts',
(err, res) => {console.log(err, res);
               client.end();
});


@Component({
  selector: 'app-test1',
  templateUrl: './test1.component.html',
  styleUrls: ['./test1.component.css']
})


export class Test1Component implements OnInit {

  constructor() {  }

  ngOnInit(): void {
  }
}

tsconfig.json

{
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": "./",
    "outDir": "./dist/out-tsc",
    "sourceMap": true,
    "declaration": false,
    "downlevelIteration": true,
    "experimentalDecorators": true,
    "module": "esnext",
    "moduleResolution": "node",
    "importHelpers": true,
    "target": "es2015",
    "lib": [
      "es2018",
      "dom"
    ],
    "types": [ "node" ],
    "typeRoots": [ "../node_modules/@types" ]
  },
  "angularCompilerOptions": {
    "fullTemplateTypeCheck": true,
    "strictInjectionParameters": true
  }
}

Please point out what went wrong

[ A note that, for this part of error

Try npm i @types/node and then add node to the types field in your tsconfig.

i did npm install @types/node --save and then added lines to tsconfig.json but error stays same ]

Answer 1

Regardless if you can even use postgresql in the browser (which you can't). To import a package like that, you have to install the types and then you can use the import statement:

npm i -D @types/pg

import { Pool, Client } from 'pg'; 

Let me just say it again though, the package pg is just for a node.js environment, not for a browser:

Non-blocking PostgreSQL client for Node.js