Avoiding Bad Angular Patterns: Best Practices for Clean and Efficient Code

Angular is a powerful front-end framework that is widely used for building web applications. However, like any software tool, it can be misused, leading to inefficient and hard-to-maintain code. In this article, we'll take a look at some bad patterns to avoid in Angular.

Overuse of NgOnInit

NgOnInit is a lifecycle hook in Angular that is called after the component has been initialized. While it's a useful tool for initializing component properties, it's often overused. Some developers put all their initialization code in NgOnInit, even if it's not related to the component's initialization. This can lead to bloated and hard-to-read code. Instead, consider using a separate method for each initialization task, or even better, delegate the initialization to a service. A code example can be found below:

// Bad code
export class ExampleComponent implements OnInit {
  ngOnInit(): void {
    this.fetchData();
    this.calculateValues();
    this.initializeForm();
  }

  private fetchData() { ... }
  private calculateValues() { ... }
  private initializeForm() { ... }
}

// Good code
export class ExampleComponent implements OnInit {
  ngOnInit(): void {
    this.fetchData();
  }

  private fetchData() {
    this.calculateValues();
    this.initializeForm();
  }

  private calculateValues() { ... }
  private initializeForm() { ... }
}

Avoid directct DOM manipulation

One of the advantages of Angular is that it abstracts away the DOM, allowing developers to focus on the application logic. However, some developers try to manipulate the DOM directly, which can lead to unpredictable results and make the code harder to maintain. Instead, use Angular's built-in directives, such as ngIf and ngFor, to manipulate the DOM declaratively.

// Bad code
export class ExampleComponent {
  constructor(private renderer: Renderer2) {}

  ngAfterViewInit() {
    const element = this.renderer.createElement('div');
    element.textContent = 'Hello, world!';
    this.renderer.appendChild(document.body, element);
  }
}

// Good code
export class ExampleComponent {
  showGreeting = true;
}

<div *ngIf="showGreeting">Hello, world!</div>

Inefficient data binding

Data binding is one of the core features of Angular, allowing components to communicate with each other and update the UI dynamically. However, it's important to use data binding efficiently. For example, using two-way data binding ([(ngModel)]) can cause performance issues if the data is updated frequently. Instead, consider using one-way data binding ({{}}) or event binding (()).

// Bad code
<input [(ngModel)]="name">

// Good code
<input [value]="name" (input)="name = $event.target.value">

Bloated templates

Angular templates can become bloated if developers try to do too much in them. For example, it's common to see templates with long lists of ngIf and ngFor directives, making them hard to read and understand. Instead, consider moving complex logic to the component or a separate service. You can also break down templates into smaller components, each responsible for a specific part of the UI.

// Bad code
<ul>
  <li *ngFor="let item of items" [ngIf]="item.isActive">
    <div [style.color]="item.color">{{ item.name }}</div>
    <button (click)="deleteItem(item)">Delete</button>
  </li>
</ul>

// Good code
<app-item-list [items]="activeItems"></app-item-list>

// app-item-list.component.html
<ul>
  <li *ngFor="let item of items">
    <app-item [item]="item"></app-item>
  </li>
</ul>

// app-item.component.html
<div [style.color]="item.color">{{ item.name }}</div>
<button (click)="deleteItem(item)">Delete</button>

Ignoring the Angular style guide

Angular provides a style guide that outlines best practices for writing clean and maintainable code. However, some developers ignore the style guide and write code in their own style. This can lead to inconsistencies in the codebase and make it harder to read and maintain. Instead, follow the Angular style guide and adopt a consistent coding style across the project.

// Bad code
export class ExampleComponent {
  private _name: string;
  get name(): string {
    return this._name;
  }
  set name(value: string) {
    this._name = value.trim().toUpperCase();
  }
}

// Good code
export class ExampleComponent {
  private _name = '';
  get name(): string {
    return this._name;
  }
  set name(value: string) {
    this._name = value.trim().toUpperCase();
  }
}

In conclusion, Angular is a powerful framework that can help you build great web applications. However, it's important to use it correctly and avoid bad patterns that can lead to inefficient and hard-to-maintain code. By following best practices and avoiding the patterns outlined in this article, you can ensure that your Angular codebase is clean, efficient, and easy to maintain.