1. Overview of MEAN Stack:

• MongoDB: NoSQL database that stores data in JSON-like documents.
• Express.js: Web application framework for Node.js, simplifying API development.
• Angular: Front-end framework for building dynamic web applications.
• Node.js: JavaScript runtime for executing server-side code.

2. MongoDB:

• Basic Commands:

db.collection.find(): Query documents.
db.collection.insertOne(): Insert a single document.
db.collection.updateOne(): Update a document.
db.collection.deleteOne(): Delete a document.

• Mongoose:
  • Use Mongoose for schema definitions and validation.
  • Example Schema:
    
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    const mongoose = require('mongoose');
    const UserSchema = new mongoose.Schema({
    name: String,
    email: String,
    password: String,
    });
    

3. Express.js:

• Basic Setup:
  
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  const express = require('express');
  const app = express();
  app.use(express.json());
  

• Routing:
  • Create routes using app.get(), app.post(), etc.
  • Use express.Router() for modular routing.
• Middleware:
  • Implement middleware for error handling, authentication, and logging.

4. Angular:

• Component Structure:
  • Use Angular CLI to generate components: ng generate component component-name.
• Services:
  • Create services for data handling and business logic.
  • Example:
    
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    import { Injectable } from '@angular/core';
    import { HttpClient } from '@angular/common/http';@Injectable({
    providedIn: 'root',
    })
    export class ApiService {
    constructor(private http: HttpClient) {}
    getData() {
    return this.http.get('api/endpoint');
    }
    }
    

• Routing:
  • Use RouterModule for navigation between components.
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  import { RouterModule, Routes } from '@angular/router';
  const routes: Routes = [{ path: 'home', component: HomeComponent }];
  

5. Node.js:

• Basic Server Setup:
  
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  const http = require('http');
  const server = http.createServer(app);
  server.listen(3000, () => {
  console.log('Server is running on port 3000');
  });
  

• APIs:
  • Build RESTful APIs and connect them to the Angular front-end.

6. Full-Stack Integration:

• API Calls: Use Angular’s HttpClient to make HTTP requests to the Express backend.
• CORS: Enable CORS in Express for cross-origin requests.
  
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  const cors = require('cors');
  app.use(cors());
  

7. Authentication:

• JWT (JSON Web Tokens):
  • Use JWT for user authentication.
  • Example:
    
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    const jwt = require('jsonwebtoken');
    const token = jwt.sign({ userId: user._id }, 'secretkey');
    

• Passport.js: Optional library for more complex authentication strategies.

It  provides a solid foundation for mastering the MEAN stack. Focus on building projects to apply these concepts, and continually explore advanced topics to enhance your expertise!
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