Using fs module
import fs from "fs"
fs.copyFile("file1.txt", "file2.txt",(err)=>{
if(err) console.log(Error happened ${err}
)
else console.log("Copied Successfully.")
})
fs.wrtieFile("message.txt", "Hello from Node Js!", (err) => {
if(err) console.log(Error happened ${err}
)
else console.log("The file has been saved.")
});
fs.readFile("message.txt", "utf-8", (err, data) => {
if(err) throw err;
else console.log(data);
});
|
node.js project initial setting
create folder (ex. intro_to_node)
npm init -y >> package.json created
npm i express nodemon
at package.json
"type": "module",
"main": "server.js",
"scripts": {
...,
"start": "nodemon server.js"
}
create server.js file
|
Node/Express Server
import express from "express"
const app = express();
const PORT = 3000;
app.listen(PORT,()=>{
console.log(The server is up and running on port ${PORT}
)
})
|
REST API
app.use(express.urlencoded({extended:true}))
//GET -- root route
app.get("/",(req,res)=>{
// console.log(req.rawHeaders)
res.send(<h1>Hello </h1>
);
})
//GET -- about route
app.get("/about",(req,res)=>{
// console.log(req.rawHeaders)
res.json({"Name":"Anu", "Title":"Instructor"});
})
//POST
app.post("/", (req,res)=>{
res.sendStatus(201)
})
//PUT
app.put("/", (req,res)=>{
res.send("Updated Successfully").sendStatus(200);
})
//DELETE
app.delete("/", (req,res)=>{
res.send("Deleted Successfully").sendStatus(200);
})
|
|
|
Ejs (Backend)
npm i ejs
import path from 'path';
import {fileURLToPath } from 'url';
const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);
//ejs
app.set("view engine", "ejs");
app.set("views", path.join(__dirname, "views"));
//POST
app.post("/",(req,res)=>{
let {num1,num2}=req.body;
let sum = parseInt(num1) + parseInt(num2);
res.render("index",{data:sum, err:"There is an error."})
})
|
Ejs (Frontend)
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Calculator</title>
</head>
<body>
<h1>Calculator</h1>
<!-- action - URL or filename or path of server side processing script -->
<!-- action - it indicates where to send the form information when the form is submitted -->
<!-- <method - post - transmits the form data in the body of the http request -->
<form action="/" method="post">
<label for="num1">Enter first number:</label>
<input type="number" name="num1" id="num1" placeholder="First Number"> <br><br>
<label for="num2">Enter second number:</label>
<input type="number" name="num2" id="num2" placeholder="Second Number"> <br><br>
<!-- <button type="submit" name="submit">Calculate</button> -->
<button>Calculate</button>
</form>
<div <% if(locals.data) {%>>
<h3>The sum is <%= data %></h3>
<% } %>
</div>
</body>
</html>
|
Axios
import axios from "axios"
app.post("/",async (req,res)=>{
const {category,difficulty} = req.body;
const URL = https://opentdb.com/api.php?amount=1&category=${category}&difficulty=${difficulty}&type=boolean
;
try{
const {data} = await axios.get(URL);
res.render("index",{resObj:data.results[0]})
}
catch(err){
console.log(The error is ${err.message}
);
res.render("index", {error_db: err.message})
}
})
|
Fetch
//GET
app.get("/",async (req,res)=>{
const URL = https://catfact.ninja/fact
;
try{
//using fetch
const response = await fetch(URL);
const data = await response.json();
res.render("index", {data: data})
}
catch(err){
console.log(The error is ${err.message}
);
res.render("index", {error: err.message})
}
})
|
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