node.js: Rest API (calculator)

3 min readApr 6, 2021

Hi people!!

Today, I will teach you how to create the calculator with basic functions.

But before starting, is important to refer to the CRUD definition.

The CRUD defintion are the acronyms for Create, Read, Update and Delete and these are the four basic operations used in relational databases.

In the ISO / SQL standard, this is the mapped abbreviation CRUD:

Create — INSERT
Read — SELECT
Update — UPDATE
Delete — DELETE

So, let’s put this into practice!!

1st step: Create a directory for the project

mkdir calculator
cd calculator

2nd step: Start the project

npm init

Remember that at the end of this step a package.json file will be created.

3rd step: Installing required packages

npm install — save hapi

4th step: Create the server (with node.js)

touch index.js

5th step: Put the following code

//Framework hapi.jsconst Hapi = require('hapi');// Machine and logical portconst host = 'localhost';const port = 8000;// Create the serverconst server = Hapi.Server({host: host,port: port});// Start the serverconst init = async () => {await server.start();console.log("Server up no porto: " + port);}// App launchinit();

6th step: Test the app running the following command…

node index.js

And the result, at this moment, is what is illustrated in this image:

The result, at this moment

7th step: Creating an about app after the init() function

server.route ({
    method: 'GET',
    path: '/ calculator / about',
    handler: function (request, h) {

        var data = {
            msg: 'Calculator API'
        };

        return data;
    }
});

8th step: Test the app again (with the command in the 6th step) and put this link in your browser:

http://localhost:8000/calculator/about

And now, the result is this:

App organization (MVC)

Our application will have this “design”:

M : for Model (code for our database model);
V : for View (layout);
C : for controllers (logical part of the app).

9th step: Create routes

mkdir routes
cd routes
touch routes.js

Before the init () function, the name file must be called. For this, it is necessary to insert the following code:

// Define routersrequire('./routes/routes')(server);

10th step and most important: enter the basic operations of the calculator

module.exports = function(server) {
//route Somaserver.route({method: 'GET',path: '/calculator/soma/{num1}/{num2}',handler: function (pedido) {const num1 = parseInt(pedido.params.num1);const num2 = parseInt(pedido.params.num2);var data = {resultado: num1 + num2};return data;}});//route Subtraçãoserver.route({method: 'GET',path: '/calculator/sub/{num1}/{num2}',handler: function (pedido){const num1 = parseInt(pedido.params.num1);const num2 = parseInt(pedido.params.num2);var data = {resultado: num1 - num2};return data;}});
//route Multiplicaçãoserver.route({method: 'GET',path: '/calculator/multi/{num1}/{num2}',handler: function (pedido){const num1 = parseInt(pedido.params.num1);const num2 = parseInt(pedido.params.num2);var data = {resultado: num1 * num2};return data;}});//route Divisãoserver.route({method: 'GET',path: '/calculator/div/{num1}/{num2}',handler: function (pedido){const num1 = parseInt(pedido.params.num1);const num2 = parseInt(pedido.params.num2);var data = {resultado: num1 / num2};return data;}});
}