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Posted on Oct 7 • Originally published at blog.stackpuz.com on Oct 3

Building an Angular CRUD App with an Express API

#express #crud #angular

CRUD operations are at the core of many web applications. This article will take you through the process of developing a CRUD app with Angular for the front end and an Express API for the back end, illustrating how these frameworks work together to create a cohesive full-stack application.

Prerequisites

Node.js
MySQL

Setup Angular project

Install Angular 18 and create a new project with the following command.

npm install -g @angular/cli@18.0.0
ng new view --minimal --routing --style css --no-standalone --ssr=false

Angular project structure

└─ src
   ├─ app
   │  ├─ app-routing.module.ts
   │  ├─ app.component.ts
   │  ├─ app.interceptor.ts
   │  ├─ app.module.ts
   │  └─ components
   │     └─ product
   │        ├─ Create.component.ts
   │        ├─ Delete.component.ts
   │        ├─ Detail.component.ts
   │        ├─ Edit.component.ts
   │        ├─ Index.component.ts
   │        └─ Product.service.ts
   ├─ index.html
   ├─ main.ts
   └─ styles.css

*This project structure will display only the files and folders that we plan to create or modify.

Angular Project files

main.ts

import { enableProdMode } from '@angular/core'
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic'

import { AppModule } from './app/app.module'

platformBrowserDynamic().bootstrapModule(AppModule).catch(e => console.error(e))

This main.ts file initializes an Angular application by bootstrapping the AppModule using the platformBrowserDynamic function. It sets up the application to run in the browser and handles any errors that occur during the bootstrapping process.

app.module.ts

import { NgModule } from '@angular/core'
import { BrowserModule } from '@angular/platform-browser'
import { FormsModule } from '@angular/forms'
import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http'
import { AppRoutingModule } from './app-routing.module'
import { AppComponent } from './app.component'
import { AppInterceptor } from './app.interceptor'

import { ProductIndex } from './components/product/Index.component'
import { ProductCreate } from './components/product/Create.component'
import { ProductDetail } from './components/product/Detail.component'
import { ProductEdit } from './components/product/Edit.component'
import { ProductDelete } from './components/product/Delete.component'

@NgModule({
  declarations: [
    AppComponent,
    ProductIndex,
    ProductCreate,
    ProductDetail,
    ProductEdit,
    ProductDelete,
  ],
  imports: [
    BrowserModule,
    AppRoutingModule,
    FormsModule,
    HttpClientModule
  ],
  providers: [
    { provide: HTTP_INTERCEPTORS, useClass: AppInterceptor, multi: true }
  ],
  bootstrap: [AppComponent]
})

export class AppModule { }

The AppModule is the main module of an Angular application. It imports core Angular modules and sets up routing with AppRoutingModule. The module declares various product-related components. It also registers AppInterceptor as an HTTP interceptor. The AppComponent is set as the bootstrap component, making it the entry point of the application.

app.component.ts

import { Component } from '@angular/core'

@Component({
  selector: 'app-root',
  template: `<router-outlet></router-outlet>`
})

export class AppComponent { }

The app.component.ts file defines the root component, AppComponent, which uses the <router-outlet> directive in its template to display routed views. The component is identified by the app-root selector and serves as the entry point for the Angular application.

app.interceptor.ts

import { Injectable } from '@angular/core';
import { HttpInterceptor } from '@angular/common/http';
import { HttpRequest, HttpErrorResponse } from '@angular/common/http'
import { Observable, throwError } from 'rxjs'
import { HttpHandler } from '@angular/common/http'
import { HttpEvent } from '@angular/common/http'

@Injectable({
  providedIn: 'root'
})

export class AppInterceptor implements HttpInterceptor {

  baseURL = 'http://localhost:8000/api'

  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(request.clone({
      url: this.baseURL + request.url,
    }))
  }
}

The AppInterceptor class is an Angular HTTP interceptor that appends a configurable baseURL to all outgoing HTTP request URLs before they are sent to the server. This allows the application to centralize and easily manage the base API endpoint.

app-routing.module.ts

import { NgModule } from '@angular/core'
import { RouterModule, Routes } from '@angular/router'
import { ProductIndex } from './components/product/Index.component'
import { ProductCreate } from './components/product/Create.component'
import { ProductDetail } from './components/product/Detail.component'
import { ProductEdit } from './components/product/Edit.component'
import { ProductDelete } from './components/product/Delete.component'

const routes: Routes = [
  { path: '', redirectTo: 'product', pathMatch: 'full' },
  { path: 'product', component: ProductIndex },
  { path: 'product/create', component: ProductCreate },
  { path: 'product/:id', component: ProductDetail },
  { path: 'product/edit/:id', component: ProductEdit },
  { path: 'product/delete/:id', component: ProductDelete }
]

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})

export class AppRoutingModule { }

The AppRoutingModule sets up routing for an Angular application, including product-related paths for listing, creating, viewing, editing, and deleting products. It also includes a route that redirects from the root path "/" to the product listing page "/product".

Create.component.ts

import { Component } from '@angular/core'
import { ActivatedRoute, Router } from '@angular/router'
import { ProductService } from './Product.service'

@Component({
  selector: 'product-create',
  template: `
    <div class="container">
      <div class="row">
        <div class="col">
          <form ngNativeValidate method="post" (submit)="create()">
            <div class="row">
              <div class="mb-3 col-md-6 col-lg-4">
                <label class="form-label" for="product_name">Name</label>
                <input id="product_name" name="name" class="form-control" [(ngModel)]="product.name" maxlength="50" />
                <span *ngIf="errors.name" class="text-danger">{{errors.name}}</span>
              </div>
              <div class="mb-3 col-md-6 col-lg-4">
                <label class="form-label" for="product_price">Price</label>
                <input id="product_price" name="price" class="form-control" [(ngModel)]="product.price" type="number" />
                <span *ngIf="errors.price" class="text-danger">{{errors.price}}</span>
              </div>
              <div class="col-12">
                <a class="btn btn-secondary" routerLink="/product">Cancel</a>
                <button class="btn btn-primary">Submit</button>
              </div>
            </div>
          </form>
        </div>
      </div>
    </div>`
})
export class ProductCreate {

  product?: any = {}
  errors?: any = {}
  constructor(private router: Router, private route: ActivatedRoute, private ProductService: ProductService) { }

  create() {
    this.ProductService.create(this.product).subscribe(() => {
      this.router.navigateByUrl('/product')
    }, (e) => {
      alert(e.error)
    })
  }
}

The ProductCreate component provides a form for creating a new product, binding input fields for name and price to a product object. On submission, it calls ProductService to create the product and navigates back to the product list. Validation errors are displayed next to the corresponding fields, and any creation errors trigger an alert.

Delete.component.ts

import { Component } from '@angular/core'
import { ActivatedRoute, Router } from '@angular/router'
import { ProductService } from './Product.service'

@Component({
  selector: 'product-delete',
  template: `
    <div class="container">
      <div class="row">
        <div class="col">
          <form ngNativeValidate method="post" (submit)="this.delete()">
            <div class="row">
              <div class="mb-3 col-md-6 col-lg-4">
                <label class="form-label" for="product_id">Id</label>
                <input readonly id="product_id" name="id" class="form-control" value="{{product.id}}" type="number" required />
              </div>
              <div class="mb-3 col-md-6 col-lg-4">
                <label class="form-label" for="product_name">Name</label>
                <input readonly id="product_name" name="name" class="form-control" value="{{product.name}}" maxlength="50" />
              </div>
              <div class="mb-3 col-md-6 col-lg-4">
                <label class="form-label" for="product_price">Price</label>
                <input readonly id="product_price" name="price" class="form-control" value="{{product.price}}" type="number" />
              </div>
              <div class="col-12">
                <a class="btn btn-secondary" routerLink="/product">Cancel</a>
                <button class="btn btn-danger">Delete</button>
              </div>
            </div>
          </form>
        </div>
      </div>
    </div>`
})
export class ProductDelete {

  product?: any = {}
  constructor(private router: Router, private route: ActivatedRoute, private ProductService: ProductService) { }

  ngOnInit() {
    this.get()
  }

  get() {
    return this.ProductService.delete(this.route.snapshot.params['id']).subscribe(data => {
      this.product = data
    }, e => {
      alert(e.error)
    })
  }

  delete() {
    this.ProductService.delete(this.route.snapshot.params['id'], this.product).subscribe(() => {
      this.router.navigateByUrl('/product')
    }, (e) => {
      alert(e.error)
    })
  }
}

The ProductDelete component in Delete.component.ts is an Angular component that handles the deletion of a product. It displays a form with read-only fields showing the product's details (ID, name, and price). When the component initializes, it fetches the product details using the product ID from the route. On form submission, the delete() method calls ProductService to delete the product and then redirects to the product list. If there's an error during deletion, an alert is shown.

Detail.component.ts

import { Component } from '@angular/core'
import { ActivatedRoute } from '@angular/router'
import { ProductService } from './Product.service'

@Component({
  selector: 'product-detail',
  template: `
    <div class="container">
      <div class="row">
        <div class="col">
          <form ngNativeValidate method="post">
            <div class="row">
              <div class="mb-3 col-md-6 col-lg-4">
                <label class="form-label" for="product_id">Id</label>
                <input readonly id="product_id" name="id" class="form-control" value="{{product.id}}" type="number" required />
              </div>
              <div class="mb-3 col-md-6 col-lg-4">
                <label class="form-label" for="product_name">Name</label>
                <input readonly id="product_name" name="name" class="form-control" value="{{product.name}}" maxlength="50" />
              </div>
              <div class="mb-3 col-md-6 col-lg-4">
                <label class="form-label" for="product_price">Price</label>
                <input readonly id="product_price" name="price" class="form-control" value="{{product.price}}" type="number" />
              </div>
              <div class="col-12">
                <a class="btn btn-secondary" routerLink="/product">Back</a>
                <a class="btn btn-primary" routerLink="/product/edit/{{product.id}}">Edit</a>
              </div>
            </div>
          </form>
        </div>
      </div>
    </div>`
})
export class ProductDetail {

  product?: any = {}
  constructor(private route: ActivatedRoute, private ProductService: ProductService) { }

  ngOnInit() {
    this.get()
  }

  get() {
    return this.ProductService.get(this.route.snapshot.params['id']).subscribe(data => {
      this.product = data
    }, e => {
      alert(e.error)
    })
  }
}

The ProductDetail component displays the details of a specific product. It retrieves the product information based on the ID from the route and shows the product's ID, name, and price in read-only fields. The component provides "Back" and "Edit" buttons for navigation. The product details are fetched and displayed when the component initializes.

Edit.component.ts

import { Component } from '@angular/core'
import { ActivatedRoute, Router } from '@angular/router'
import { ProductService } from './Product.service'

@Component({
  selector: 'product-edit',
  template: `
    <div class="container">
      <div class="row">
        <div class="col">
          <form ngNativeValidate method="post" (submit)="edit()">
            <div class="row">
              <div class="mb-3 col-md-6 col-lg-4">
                <label class="form-label" for="product_id">Id</label>
                <input readonly id="product_id" name="id" class="form-control" [(ngModel)]="product.id" type="number" required />
                <span *ngIf="errors.id" class="text-danger">{{errors.id}}</span>
              </div>
              <div class="mb-3 col-md-6 col-lg-4">
                <label class="form-label" for="product_name">Name</label>
                <input id="product_name" name="name" class="form-control" [(ngModel)]="product.name" maxlength="50" />
                <span *ngIf="errors.name" class="text-danger">{{errors.name}}</span>
              </div>
              <div class="mb-3 col-md-6 col-lg-4">
                <label class="form-label" for="product_price">Price</label>
                <input id="product_price" name="price" class="form-control" [(ngModel)]="product.price" type="number" />
                <span *ngIf="errors.price" class="text-danger">{{errors.price}}</span>
              </div>
              <div class="col-12">
                <a class="btn btn-secondary" routerLink="/product">Cancel</a>
                <button class="btn btn-primary">Submit</button>
              </div>
            </div>
          </form>
        </div>
      </div>
    </div>`
})
export class ProductEdit {

  product?: any = {}
  errors?: any = {}
  constructor(private router: Router, private route: ActivatedRoute, private ProductService: ProductService) { }

  ngOnInit() {
    this.get()
  }

  get() {
    return this.ProductService.edit(this.route.snapshot.params['id']).subscribe(data => {
      this.product = data
    }, e => {
      alert(e.error)
    })
  }

  edit() {
    this.ProductService.edit(this.route.snapshot.params['id'], this.product).subscribe(() => {
      this.router.navigateByUrl('/product')
    }, (e) => {
      alert(e.error)
    })
  }
}

The ProductEdit component allows users to edit an existing product. It retrieves the product details using the product ID from the route and displays them in a form with editable fields for name and price. On form submission, it updates the product via ProductService and navigates back to the product list. Any errors during fetching or updating are shown as alerts, and validation errors are displayed next to the relevant fields.

Index.component.ts

import { Component } from '@angular/core'
import { Router, NavigationEnd } from '@angular/router'
import { ProductService } from './Product.service'

@Component({
  selector: 'product-index',
  template: `
    <div class="container">
      <div class="row">
        <div class="col">
          <table class="table table-striped table-hover">
            <thead>
              <tr>
                <th>Id</th>
                <th>Name</th>
                <th>Price</th>
                <th>Actions</th>
              </tr>
            </thead>
            <tbody>
              <tr *ngFor="let product of products">
                <td class="text-center">{{product.id}}</td>
                <td>{{product.name}}</td>
                <td class="text-center">{{product.price}}</td>
                <td class="text-center">
                  <a class="btn btn-secondary" routerLink="/product/{{product.id}}" title="View"><i class="fa fa-eye"></i></a>
                  <a class="btn btn-primary" routerLink="/product/edit/{{product.id}}" title="Edit"><i class="fa fa-pencil"></i></a>
                  <a class="btn btn-danger" routerLink="/product/delete/{{product.id}}" title="Delete"><i class="fa fa-times"></i></a>
                </td>
              </tr>
            </tbody>
          </table>
          <a class="btn btn-primary" routerLink="/product/create">Create</a>
        </div>
      </div>
    </div>`
})

export class ProductIndex {

  products?: any[]
  constructor(public router: Router, private ProductService: ProductService) { }

  ngOnInit() {
    this.get()
  }

  get() {
    this.ProductService.get().subscribe(data => {
      this.products = data
    }, e => {
      alert(e.error)
    })
  }
}

The ProductIndex component displays a list of products in a table format. It fetches the list of products from ProductService on initialization and shows each product's ID, name, and price, with action buttons for viewing, editing, and deleting each product. It also includes a button to navigate to the product creation page.

Product.service.ts

import { Injectable } from '@angular/core'
import { HttpClient } from '@angular/common/http'
import { Observable } from 'rxjs'

@Injectable({
  providedIn: 'root'
})

export class ProductService {

  constructor(private http: HttpClient) { }

  get(id?: any): Observable<any> {
    if (id) {
      return this.http.get(`/products/${id}`)
    }
    else {
      return this.http.get('/products' + location.search)
    }
  }

  create(data?: any): Observable<any> {
    if (data) {
      return this.http.post('/products', data)
    }
    else {
      return this.http.get('/products/create')
    }
  }

  edit(id: any, data?: any): Observable<any> {
    if (data) {
      return this.http.put(`/products/${id}`, data)
    }
    else {
      return this.http.get(`/products/${id}`)
    }
  }

  delete(id: any, data?: any): Observable<any> {
    if (data) {
      return this.http.delete(`/products/${id}`)
    }
    else {
      return this.http.get(`/products/${id}`)
    }
  }
}

The ProductService uses Angular's HttpClient to perform the relevant HTTP requests for product management. It provides methods to:

get(id?): Fetch product details by ID or a list of products if no ID is provided.
create(data?): Create a new product if data is provided, otherwise fetch the create product page.
edit(id, data?): Update a product by ID if data is provided, otherwise fetch product details for editing.
delete(id, data?): Delete a product by ID if data is provided, otherwise fetch product details for confirmation.

styles.css

.container {
  margin-top: 2em;
}

.btn {
  margin-right: 0.25em;
}

The CSS adjusts the layout by adding space above the container and spacing out buttons horizontally.

index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width,initial-scale=1">
  <link href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap/5.3.3/css/bootstrap.min.css" rel="stylesheet">
  <link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.5.0/css/all.min.css" rel="stylesheet">
</head>
<body>
  <app-root></app-root>
</body>
</html>

The HTML serves as the main entry point for an Angular application, including Bootstrap for styling, Font Awesome for icons, and <app-root> as the placeholder for the Angular app.

Setup Express API project

npm install express mysql2 sequelize cors

Create a testing database named "example" and execute the database.sql file to import the table and data.

Express API Project structure

├─ config.js
├─ index.js
├─ router.js
├─ db.js
├─ controllers
│  └─ ProductController.js
└─ models
   └─ Product.js

Express API Project files

config.js

module.exports = {
  host: '127.0.0.1',
  port: 3306,
  user: 'root',
  password: '',
  database: 'example',
  dialect: 'mysql'
}

This file holds the configuration details for connecting to the database.

db.js

const Sequelize = require('sequelize')
const config = require('./config')

module.exports = new Sequelize(config.database, config.user, config.password, {
  host: config.host,
  port: config.port,
  dialect: config.dialect,
  define: {
    timestamps: false,
    freezeTableName: true
  }
})

This db.js file initializes and exports a Sequelize instance using configuration details from a config.js file. It connects to the database with specified credentials and options, disabling automatic timestamps and preserving table names as defined.

router.js

const express = require('express')
const product = require('./controllers/ProductController.js')

module.exports = express.Router().use('/products', express.Router()
  .get('/', product.getProducts)
  .get('/:id', product.getProduct)
  .post('/', product.createProduct)
  .put('/:id', product.updateProduct)
  .delete('/:id', product.deleteProduct)
)

This router.js file configures Express routes for product management. It exports a router that handles GET, POST, PUT, and DELETE requests under the /products path, linking each route to a corresponding method in the ProductController.

index.js

const express = require('express')
const cors = require('cors')
const router = require('./router.js')

const app = express()
app.use(cors())
app.use(express.json())
app.use('/api', router)
app.listen(8000)

This index.js file sets up an Express server. The app is configured to use CORS for handling cross-origin requests and to parse JSON request bodies. The router is mounted on the /api path, handling all API routes defined in the router module. Finally, the server listens for incoming connections on port 8000.

product.js

const Sequelize = require('sequelize')
const db = require('../db')

module.exports = db.define('Product', {
  id: {
    type: Sequelize.INTEGER,
    primaryKey: true,
    autoIncrement: true
  },
  name: Sequelize.STRING,
  price: Sequelize.DECIMAL
})

This product.js file defines a Sequelize model for a Product entity. The model is defined with three fields: id, (a primary key that auto-increments), name, price.The model is then exported for use in other parts of the application.

ProductController.js

const Product = require('../models/Product')

exports.getProducts = async (req, res) => {
  let products = await Product.findAll()
  res.send(products)
}

exports.getProduct = async (req, res) => {
  let product = await Product.findByPk(req.params.id)
  res.send(product)
}

exports.createProduct = async (req, res) => {
  let product = { ...req.body }
  let created = await Product.create(product)
  res.send(created)
}

exports.updateProduct = async (req, res) => {
  let product = { ...req.body }
  await Product.update(product, { where: { id: req.params.id } })
  let updated = await Product.findByPk(req.params.id)
  res.send(updated)
}

exports.deleteProduct = async (req, res) => {
  await Product.destroy({ where: { id: req.params.id } })
  res.end()
}

The ProductController.js file defines several asynchronous handler functions for managing Product entities in a Express API application using Sequelize.

getProducts Retrieves and sends a list of all products.
getProduct Fetches and sends a single product based on its ID.
createProduct Creates a new product from the request body.
updateProduct Updates an existing product with the data from the request body.
deleteProduct Deletes a product by its ID.

Run projects

Run Angular project

npm start

Run Express API project

node index.js

Open the web browser and goto http://localhost:4200

You will find this product list page.

Testing

Click the "View" button to see the product details page.

Click the "Edit" button to modify the product and update its details.

Click the "Submit" button to save the updated product details.

Click the "Create" button to add a new product and input its details.

Click the "Submit" button to save the new product.

Click the "Delete" button to remove the previously created product.

Click the "Delete" button to confirm the removal of this product.

Conclusion

In conclusion, we have learned how to create a basic Angular project with components, views, and routing, while setting up an Express API server as the backend. By using Sequelize for database operations, we built a dynamic front-end that seamlessly interacts with a robust backend. This setup provides a strong foundation for developing modern, full-stack web applications.

Source code: https://github.com/stackpuz/Example-CRUD-Angular-18-Express-4

Create an Angular CRUD App in Minutes: https://stackpuz.com

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