nodejs

Question 1

Get started with Nodejs

Answer 1

Nodejs is modular and that is its power.

The NPM helps tap into that modularity.

Question 2

What to write to define destination of current directory?

Answer 2

__dirname

Question 3

Initialize nodejs

Answer 3

npm init

Question 4

express.js - package of nodejs

Answer 4

npm install express

const express = require(‘express’);

const app = express( );

Question 5

body-parser - package of nodejs

USED TO PARSE DATA AND RECEIVE THEM IN USABLE FORM

Answer 5

npm install body-parser

const bodyParser = require(‘body-parser’);

//if app is the const holding the value of express( )

app.use( bodyParser.urlencoded( {extended: true} ) );

Question 6

START A SERVER

Answer 6

app.listen(port here, console command here);

Example –
app.listen( 8080, console.log(‘Server has started on port 8080’));

Question 7

Route websites using Express.js

Respond to designated path

Answer 7

app.get( ‘/route here’ , function (req, res)
{
res.send(‘’)
});

OR

app.get( ‘/route here’ , function (req, res)
{
res.sendFile(__dirname + ‘html document here’);
});

Question 8

POST result to the Submitted action

Answer 8

apt.post('/destination page', function (req, res)
                                                {
                                                     var variable = parseFloat(req.body.nameOfSubmittedValue);
                                                      // calculations ---
                                                     res.send('HTML result to send');
                                                 } );

Question 9

Access API with HTTPS module of nodejs

Answer 9

const https = require(‘https’);

https.get ('url here' , function (request, response)
                                     {
                                            console.log(response.statusCode);
                                            response.on( 'data' , function (data) { const someData = JSON.parse(data); console.log(someData) } );

The first parameter ‘data’ shouldnt be change for response.on( ) if we want to receive data.

Question 10

JSON.parse && JSON.stringify

Answer 10

.parse unpacks the JSON file and structures in a more readable form.

.stringify packs the JSON and compresses it to reduce file size.

Question 11

Encoding character of response.send

Answer 11

response.setHeader(“Content-Type”, “text/html ; charset=utf-8”);

Question 12

POST response for the SUBMIT input

Answer 12

response.send(‘text/html here’) sends a text or html in response to submit input

For multi-line response -

response. write(‘text/html here’)
response. write(‘text/html here’)
response. send( )

Question 13

Redirect website

Answer 13

When a post method is called –

app.post ( ‘some path here’, (req, res) => { res.redirect (‘redirect path here’); } )

Question 14

Dynamic Port selection for Heroku

Answer 14

Documentation on heroku suggests we listen to following

app.listen ( process.env.PORT )

OR

app.listen ( process.env.PORT || 3000 )
[ This allows us to listen to the port dynamically according to heroku’s allotment and also listen to 3000 at all times]

Question 15

Pointing to static files like CSS and Javascript

Answer 15

1) Make a public folder in the root.
2) Require express in your nodejs file.

3) app.use( express.static (‘public’) );

Question 16

CSS for HTML through nodejs

Answer 16

You have to make a ‘public’ folder so expressjs can access ‘root’ of the project. For expressjs, ‘public’ is the root of the project, and not the actual root.

Oh, also tell express about this folder by —

app.use(express.static(“public”));

Question 17

How does .post method work?

Answer 17

When HTML form passes an input, it has an action=”path1 here” property. This is the path, where it sends the input.

In the server, app.post(“path1 here”) will capture that input and then bodyparser maybe used to parse the input into usuable variable.

For EJS—–
To add to this - the button type=”submit” can have a name and value declared by name=”name here” and value=”value here” inside the opening tags of button.

Example -

(angl)button type=’button’ name=”hereName” value=”hereValue”(angl_clos) Text here (angl)/button(angl_clos)

so when this submit an input - bodyparser will intercept object with name of variable and its value + another property saying
“hereName: hereValue”

This can be used to do more specific operations like adding variables to different array depending on value of submit button which can be changed dynamically now thanks to ejs.

Question 18

How do node modules work?

[exports.function]

Answer 18

We can ‘require’ a local javascript like we require modules like express and bodyparser that we install through npm.

These local javascript can be exported using a method called ‘module’.

Module helps to export an external function into another javascript.

So –> module.exports returns an object when called.

Hence we can have multiple functions tied to this date. Like —

module. exports.someFunction = function ( ) { //code here; }
module. exports.someFunction2 = function ( ) { //code here; }

and the specific function can now be executed externally after ‘requiring’ the javascript and calling myVar.someFunction( );
or calling myVar.someFunction2 ( );

Btw, ‘module.exports.function’ can be written as just ‘exports.function’ and it would mean the same thing.

Question 19

Express Routing Parameters

Answer 19

Helps in quick routing setup without needing to write multiple app.get( ) parameters multiple times

app.get(‘ /:enter_new_path_here ‘, function(request, response) { // code here for template }

Question 20

Lodash module

Answer 20

npm install lodash

var _ = require(‘lodash’);

API documentation : https://lodash.com/docs/4.17.15

This is a very handy module which can do a number of things. Among which is a feature that can turn any type of casing into lower case title with appropriate spacing.

For exmaple - we want to lowerCase a title smartly -

_.lowerCase('--Foo-Bar--');
// => o/p - 'foo bar'

_.lowerCase('fooBar');
// => 'foo bar'

_.lowerCase('\_\_FOO_BAR\_\_');
// => 'foo bar'