Create an API via NestJS Part I

1. Setup the project

Firstly we need to install CLI tools for creating the scaffold.

I use the npm for this because the yarn has a bug with node engine version:

npm i -g @nestjs/cli

After that, we must create a new boilerplate project:

nest new {type your project name here}

This wizard will ask you about which package manager is you prefer:

Which package manager would you ❤️ to use?

I prefer yarn and in this article, I had chosen it.

When installation will be done you will see:

bash output

Now we can setting up Prettier:

cd {YourProjectName}
vim .prettierrc

In this file we must wrote something like this:

"useTabs": false,
"tabWidth": 2,
"singleQuote": true,
"trailingComma": "all",
"semi": true,
"jsxBracketSameLine": true,
"bracketSpacing": true,
"arrowParens": "avoid"

Finally we can start project and have see Hello World message, let's try:

cd {YourProjectName}

yarn run start 

When you will see:

bash output

You can check how it's work into your browser on page http://localhost:3000

And now you probably get stuck with :3000, what does it mean? Yeah, it is port of your server, it can be change in src/main.ts file line 6:


It's not beautiful enough, what we have to do if we'll want change it dynamically? Yes, we must pull it into enviroment variable. But how?

The dotenv packagecomes to our aid, let's add it:

yarn add dotenv

and setup it:

touch .env && echo "PORT=4000" > .env

Now we can use environment variables in our project just like this:


What is we have done?

  1. Imported package dotenv/config into main.ts
  2. Created constant with the value from .env file or, if it's empty, 8080
  3. Used it in the function app.listen()

Now we can check this, go to http://localhost:4000 if we have done everything right, we'll see the "Hello World" message.

Not forget to reload your server, if you want use hotreload you have to use yarn run start:dev instead of yarn run start

Looks good, but how we can know witch PORT used now? We have to write a Logger for our server! Open main.ts file and add this string after app.listen() function:


Now, after you start your server you must see message like this:

bash output

2. Install packages to using DataBase

JS packages

In order to work with the database, we need to install some packages:

yarn add pg typeorm @nestjs/typeorm

OS packages

For development we also need Postgres Server and PgAdmin tool, if you are use Ubuntu 18.04 you have to install it this way:

  1. cd /etc/apt/sources.list.d/
  2. sudo touch pgdg.list
  3. echo "deb bionic-pgdg main" > pgdg.list
  4. wget --quiet -O - | sudo apt-key add -
  5. sudo apt-get update
  6. sudo apt install postgresql-11 postgresql-client-11 pgadmin4

For another OS check this page.

After installation instruction:

  1. Edit the pg_hba.conf file: sudo vim /etc/postgresql/11/main/pg_hba.conf
  2. Change the line local all postgres peer to local all postgres trust
  3. Restart postgresql service: sudo service postgresql restart
  4. Log in into DB and change password:
    1. psql -U postgres
    2. In the postgres=# prompt: ALTER USER postgres with password ‘new-password’;
  5. Revert the changes:
    1. sudo vim /etc/postgresql/11/main/pg_hba.conf change line from trust to md5
    2. Restart postgresql service: sudo service postgresql restart

3. Setup DataBase

Create a new DataBase

    • Login to Postgres
      • psql -U postgres
    • Create a new DB
      • create database quiz;
      • \q - to quit from psql

    Connect the DataBase to your project

      Create ORM config file

        • touch ormconfig.js
        • Edit this file as follows
      Where fields "host", "username", "password", "database" is your credentials to database which can set in .env file
        • Set credentials in .env file:

      Import ORM module:

        • Go to file src/app.module.ts
        • Add the following lines:

      Start working with DB

      Create entities

      1. Create entnities structure
        • mkdir src/quiz
        • cd src/quiz/ && touch quiz.entity.ts
      2. Edit quiz.entity.ts as follow:

        Check if it work

        Star your server via yarn run start . Then you must see output like that:

        bash output

        Now browse the DB:

          • psql -U postgres - connect to db server
          • \c quiz - open db called quiz
          • \dt - describe tables within

        If everything is ok, you should see:

        bash output