10 Common Mistakes to Avoid While Building An Efficient Angular Application
Tags: angular, beginners, ui, webdev
Published: 2023-09-11 10:53:37

Developing an efficient Angular website can be a rewarding experience, but it's easy to stumble into these common mistakes. In this article, we'll explore some of these mistakes and provide clear explanations and examples to help you avoid them.


## 1: Neglecting Module Organization

**Explanation:** Angular encourages the use of modules to organize your application. Neglecting this can lead to a disorganized and hard-to-maintain codebase.

**Example:** Let's say you have a shopping website. Instead of creating separate modules for features like product listing, cart, and user authentication, you put everything in a single module. This can lead to a tangled mess of code.

```typescript
// All components and services in one app module
@NgModule({
  declarations: [ProductListComponent, CartComponent, LoginComponent],
  // ...
})
export class AppModule { }
```

**Solution:** Organize your application into feature modules. Create a `ProductModule`, `CartModule`, and `AuthModule`, each containing their respective components and services.

```typescript
// Organized feature modules
@NgModule({
  imports: [ProductModule, CartModule, AuthModule],
  // ...
})
export class AppModule { }
```


## 2: Ignoring Lazy Loading

**Explanation:** Failing to implement lazy loading can result in larger initial load times and decreased performance.

**Example:** Imagine all modules are eagerly loaded in your application. When a user accesses the homepage, every feature module is loaded, including those they might not use immediately.

```typescript
// Eagerly loading modules
@NgModule({
  imports: [ProductModule, CartModule, AuthModule],
  // ...
})
export class AppModule { }
```

**Solution:** Utilize lazy loading to load modules only when they are needed. This improves the initial load time.

```typescript
const routes: Routes = [
  { path: 'products', loadChildren: () => import('./product/product.module').then(m => m.ProductModule) },
  { path: 'cart', loadChildren: () => import('./cart/cart.module').then(m => m.CartModule) },
  { path: 'auth', loadChildren: () => import('./auth/auth.module').then(m => m.AuthModule) },
];
```


## 3: Overusing ngIf and ngFor

**Explanation:** Excessive use of structural directives like `*ngIf` and `*ngFor` can lead to performance issues.

**Example:** Consider a list of products. If you use `*ngIf` to display each product individually, Angular will create and destroy DOM elements for each product, causing unnecessary overhead.

```html
<!-- Using *ngIf for each product -->
<div *ngFor="let product of products">
  <div *ngIf="product.isVisible">{{ product.name }}</div>
</div>
```

**Solution:** Instead of using `*ngIf` for each item, filter your data in the component to exclude hidden items before rendering.

```html
<!-- Filtering data in component -->
<div *ngFor="let product of visibleProducts">
  {{ product.name }}
</div>
```


## 4: Neglecting Data Prefetching

**Explanation:** An alternative mistake regarding data retrieval is neglecting to prefetch data when it's likely to be needed in the near future. But be careful and observe the difference between data prefetching and lazy loading.

**Example:**

Suppose your e-commerce site doesn't prefetch product details when a user hovers over a product card. Instead, it makes an HTTP request only when the user clicks on a product.

```typescript
// ProductComponent.ts
onProductClick(productId: string) {
  this.http.get(`/api/products/${productId}`).subscribe((data) => {
    this.productData = data;
  });
}
```

**Solution:** Prefetch data proactively to enhance user experience.

```typescript
// Better Approach: Prefetch product data on hover
// ProductComponent.ts
onProductHover(productId: string) {
  this.http.get(`/api/products/${productId}`).subscribe((data) => {
    this.preloadedData = data;
  });
}

onProductClick() {
  this.productData = this.preloadedData;
}
```


## 5: Not Handling Error Responses

**Explanation:** Failing to handle error responses properly can lead to a poor user experience and leave your application vulnerable.

**Example:** You make an HTTP request, but you don't handle errors, so if the server returns an error status, the application crashes.

```typescript
// Not handling HTTP errors
this.http.get('/api/products').subscribe(
  (data) => {
    // Handle successful response
  }
);
```

**Solution:** Always include error handling to gracefully manage HTTP errors and provide feedback to users.

```typescript
// Handling HTTP errors
this.http.get('/api/products').subscribe(
  (data) => {
    // Handle successful response
  },
  (error) => {
    // Handle errors, e.g., show an error message
    console.error('HTTP Error:', error);
  }
);
```


## 6: Not Implementing Routing Guards

**Explanation:** Neglecting to use Angular routing guards can lead to unauthorized access or navigation issues in your application.

**Example:** You have a route that should be accessible only to authenticated users, but you don't implement a route guard, allowing anyone to access it.

```typescript
const routes: Routes = [
  { path: 'dashboard', component: DashboardComponent },
  // ...
];
```

**Solution:** Implement route guards to control access to routes and protect sensitive parts of your application.

```typescript
// Implementing an authentication guard
const routes: Routes = [
  { path: 'dashboard', component: DashboardComponent, canActivate: [AuthGuard] },
  // ...
];
```


## 7: Not Utilizing OnPush Change Detection

**Explanation:** Neglecting the OnPush change detection strategy can lead to inefficient rendering and decreased performance in your Angular components.

**Example:** You have a component that doesn't utilize the OnPush strategy, causing unnecessary re-renders even when the input properties haven't changed.

```typescript
@Component({
  selector: 'app-product',
  templateUrl: './product.component.html',
})
export class ProductComponent {
  @Input() product: Product;
  // ...
}
```

**Solution:** Enable the OnPush change detection strategy to optimize component rendering.

```typescript
// Using OnPush change detection strategy
@Component({
  selector: 'app-product',
  templateUrl: './product.component.html',
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class ProductComponent {
  @Input() product: Product;
  // ...
}
```


## 8: Overusing ng-container

**Explanation:** Using too many `ng-container` elements can make your templates complex and harder to understand.

**Example:** You have nested `ng-container` elements to conditionally render content, making the template difficult to read.

```html
<ng-container *ngIf="condition">
  <ng-container *ngIf="anotherCondition">
    <!-- Content -->
  </ng-container>
</ng-container>
```

**Solution:** Simplify your templates by using regular HTML elements when possible.

```html
<!-- Simplified template -->
<div *ngIf="condition">
  <div *ngIf="anotherCondition">
    <!-- Content -->
  </div>
</div>
```


## 9: Not Optimizing for Mobile

**Explanation:** Failing to optimize your Angular website for mobile devices can result in a poor user experience on smartphones and tablets, so make sure you make your website responsive.

**Example:** Your website layout and design don't adapt well to smaller screens, making it challenging for mobile users to navigate.

```css
.container {
  width: 1200px;
  /* ... */
}
```

**Solution:** Implement responsive design techniques using CSS media queries to ensure your website looks and functions well on various screen sizes. Avoid mentioning the sizes in absolute units (ex: in, px) and use relative units (ex: em, rem, %) where ever possible.

```css

.container {
  max-width: 100%;
  /* ... */
}
```


## 10: Ignoring SEO Best Practices

**Explanation:** Neglecting search engine optimization (SEO) best practices can result in poor search engine rankings and reduced discoverability.

**Example:** Your Angular app doesn't have proper meta tags, semantic HTML, or server-side rendering, making it less SEO-friendly.

```html
<!DOCTYPE html>
<html>
<head>
  <!-- Missing meta tags and SEO-related elements -->
</head>
<body>
  <!-- Angular app content -->
</body>
</html>
```

**Solution:** Implement SEO best practices by adding meta tags, using semantic HTML elements, and considering server-side rendering (e.g., Angular Universal) for improved SEO.

```html
<!-- Correct: SEO-optimized HTML -->
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Your Page Title</title>
  <meta name="description" content="Your page description">
  <!-- Other SEO-related meta tags -->
</head>
<body>
  <!-- Angular app content -->
</body>
</html>
```

By addressing the above common things related to change detection, template complexity, responsive design, and SEO, you can create more efficient, user-friendly, and discoverable Angular websites.

Thank's for your time, see you soon in another one :)