My backend journey..........
Learnings from day 1 :
executable path for node.js
file path of our files in the directory
require() Module.exports()
library of packages command line tool FIGLET node modules - contains a package of all the dependencies of our project. package-lock.json - contains the exact version of all the dependencies. package.json
The package.json file contains descriptive and functional metadata about a project, such as a name, version and dependencies
command - npm init command is used to initialize our own package npm i -g "package name " - command is used to install a package globally npm link "package name " - command is used to link the current directory with the global directory to share the info inside packages from one place to another place.
Important note - If we are using import and export features in our project then we have to add a key:value pair named as [type:"module"] in the SAME directory.
Learnings from day : 2
A node.js web application framework that helps us to make web applications. It is used in server side programmming.
Main features:
- Listen for the incoming requests.
- Parse (Node.js)
- Match response with routes. example - https:\hariom.com\info
- Sending Suitable Response.
- defining a port const port = 8080
/* ports are the logical endpoints of a network connection that is used to exchange information between a web server and a web client.*\
- requiring express
const express = require("express");
- listening to requests using routes ('/')
app.get('/hello',(req,res)=>{
res.send("hello world");
})
- Listening to the server using the port defined.
app.listen(port,()=>{
console.log("server is running on the port",port);
})
- Sendig responses
app.use((req,res)=>{ console.log("response received"); })
installation command - npm i nodemon
Syntax : nodemon file.js
Path parameters are the variables that acts as a path varible used to reach a particular path.
syntax
app.get('/:username/:age',(req,res)=>{
let {username,age} = req.params;
//req.params means the parameters that are passed in the path and it is returned as an object.
let userPage = (`this is a page for ${username} and age : ${age}`);
res.send(userPage);
console.log(userPage);
})
Query strings are the additional information passed in the path which is stored in the "req" object of app.get() .
Syntax
app.get('/search',(req,res)=>{
let {search} = req.query;
console.log(search);
res.send(req.query);
})
EJS is a simple templating language that let's you generate HTML markup with plane Javascript. Note - Express already requires ejs so there is no need to require the ejs again. View package is used to show or render the templates. Inorder to render the templates, express by default looks for a " views " folder in ejs directory.All the templates will be present there in the views folder. If we want to render ejs file from the root directory which is the parent directory of our ejs folder which contains views folder then we have to write
const path = require("path");
Tags
<% 'Scriptlet' tag, for control-flow, no output <%_ ‘Whitespace Slurping’ Scriptlet tag, strips all whitespace before it <%= Outputs the value into the template (HTML escaped) <%- Outputs the unescaped value into the template <%# Comment tag, no execution, no output <%% Outputs a literal '<%' %> Plain ending tag -%> Trim-mode ('newline slurp') tag, trims following newline _%> ‘Whitespace Slurping’ ending tag, removes all whitespace after it
If we want to add extra css and js in our code then we can create a public folder where we can store our files and use the public folder using the given syntax :
app.use(express.static(path.join(__dirname,"/public")))
(SubTemplate)
Includes are relative to the template with the include call. (This requires the 'filename' option.) For example if you have "./views/users.ejs" and "./views/user/show.ejs" you would use <%- include('user/show'); %>.
You'll likely want to use the raw output tag (<%-) with your include to avoid double-escaping the HTML output.
-
<% users.forEach(function(user){ %>
<%- include('user/show', {user: user}); %>
<% }); %>
#Learnings of the day 3
*GET
=> used to get some responses =>data sent in query strings (limited,string data & visible in URL)
*POST
=> Used to POST something (for create/Write/Update) => Data sent via request body (any type of data)
#FORM METHODS => get => post
~ set up post request route to get some responses ~ parse post request data
Syntax
//if express is receiving an urlencoded data then it will automatically understand the format of that data by writing the below line
app.use(express.urlencoded({extended:true})); app.use(express.json());
To structure your code
Prototypes are the mechanism by which Javascript objects inherit features from one another. It is like a single template object that all object inherit methods and properties from without having their own copy.
arr.proto(reference) Array.prototype(actual object) String.prototype JS OOPS 11 (Qs).pdf
OOPS IN JAVASCRIPT
REST is an architectural style that defines a set of constraints to be used for creating web services. CRUD OPERATIONS
CREATING RESTFUL API'S EXAMPLE - QUORA POST
res.redirect(url) => redirects from a currect page,form etc to the entered path in GET response.
There is package in express which is used to generate universally unique id's when we are implementing functionalities like adding accounts, payment receipts, course id, meetings id and etc.
app.patch('/posts/:id',(req,res)=>{
}))
app.patch() method uses two parameters like a key:value pair in which in the request parameter where we have to specify the key data which is present in our code and then we can update the content inside that particular parameter but that parameter entered should match the parameter value in our dataset.
html forms only supports get and post requests that why inorder to user put,patch,delete etc. we have to install a npm package
command to install that package
npm i method-override
Override using a query value To use a query string value to override the method, specify the query string key as a string argument to the methodOverride function. To then make the call, send a POST request to a URL with the overridden method as the value of that query string key. This method of using a query value would typically be used in conjunction with plain HTML
elements when trying to support legacy browsers but still use newer methods.var express = require('express') var methodOverride = require('method-override') var app = express()
// override with POST having ?_method=DELETE app.use(methodOverride('_method')) Example call with query override using HTML :
Delete resource#Finally RESTFUL API'S ARE COMPLETED and let's move towards dbms integration with the backend.🔥🔥🔥