Why performance tuning matters in Angular - See It in Action

Why performance tuning matters

📖 Scenario: You are building a simple Angular app that shows a list of products. The list can get very long, so performance tuning is important to keep the app fast and smooth.

🎯 Goal: Create a basic Angular component that displays a list of products. Then add a configuration to limit how many products show at once. Finally, implement a simple filter to only show products with a price above a certain value. This will demonstrate why performance tuning matters by controlling how much data the app handles.

📋 What You'll Learn

Create an Angular standalone component named ProductListComponent

Initialize a list of exactly 6 products with name and price

Add a variable minPrice to filter products by price

Use an Angular *ngFor directive to display filtered products

Add a simple input to change minPrice dynamically

💡 Why This Matters

🌍 Real World

Filtering and limiting data shown in a user interface is common in real apps to keep them fast and responsive.

💼 Career

Understanding how to tune performance by controlling data flow and rendering is a key skill for Angular developers working on scalable applications.

1

Set up the product list data

Create a standalone Angular component called ProductListComponent. Inside it, create a variable products that is an array of objects with these exact entries: { name: 'Laptop', price: 1200 }, { name: 'Phone', price: 800 }, { name: 'Tablet', price: 450 }, { name: 'Monitor', price: 300 }, { name: 'Keyboard', price: 100 }, { name: 'Mouse', price: 50 }.

Angular

import { Component } from '@angular/core';

@Component({
  selector: 'app-product-list',
  standalone: true,
  template: `
    
  `
})
export class ProductListComponent {
  // Your code here
}

Hint

Remember to use products = [ ... ] inside the component class with the exact product objects.

2

Add a minimum price filter variable

Inside the ProductListComponent class, add a variable called minPrice and set it to 0. This will be used to filter products by price.

Angular

import { Component } from '@angular/core';

@Component({
  selector: 'app-product-list',
  standalone: true,
  template: `
    
  `
})
export class ProductListComponent {
  products = [
    { name: 'Laptop', price: 1200 },
    { name: 'Phone', price: 800 },
    { name: 'Tablet', price: 450 },
    { name: 'Monitor', price: 300 },
    { name: 'Keyboard', price: 100 },
    { name: 'Mouse', price: 50 }
  ];
  // Add minPrice variable here
  // Your code here
}

Hint

Just add minPrice = 0; inside the component class.

3

Filter products by minimum price in the template

In the component's template, use an Angular *ngFor directive to loop over products filtered by minPrice. Only show products where product.price >= minPrice. Display each product's name and price inside a <li> element.

Angular

import { Component } from '@angular/core';

@Component({
  selector: 'app-product-list',
  standalone: true,
  template: `
    
      
    
  `
})
export class ProductListComponent {
  products = [
    { name: 'Laptop', price: 1200 },
    { name: 'Phone', price: 800 },
    { name: 'Tablet', price: 450 },
    { name: 'Monitor', price: 300 },
    { name: 'Keyboard', price: 100 },
    { name: 'Mouse', price: 50 }
  ];
  minPrice = 0;
}

Hint

Use *ngFor="let product of products.filter(product => product.price >= minPrice)" inside the <li> tag.

4

Add input to change minimum price dynamically

Add an <input> element above the product list in the template. Bind its value to minPrice using Angular's two-way binding syntax [(ngModel)]. This allows the user to change minPrice and see the filtered products update live. Also, add FormsModule to the component's imports.

Angular

import { Component } from '@angular/core';
import { FormsModule } from '@angular/forms';

@Component({
  selector: 'app-product-list',
  standalone: true,
  imports: [FormsModule],
  template: `
    
    
       product.price >= minPrice)">
        {{ product.name }} - ${{ product.price }}
      
    
  `
})
export class ProductListComponent {
  products = [
    { name: 'Laptop', price: 1200 },
    { name: 'Phone', price: 800 },
    { name: 'Tablet', price: 450 },
    { name: 'Monitor', price: 300 },
    { name: 'Keyboard', price: 100 },
    { name: 'Mouse', price: 50 }
  ];
  minPrice = 0;
  // Your code here
}

Hint

Import FormsModule and add it to imports. Then add an <input> with [(ngModel)]="minPrice" and an aria-label for accessibility.

Practice

1. Why is performance tuning important in Angular applications?

easy

A. It changes the app's color scheme.

B. It adds more features automatically.

C. It reduces the size of the Angular framework.

D. It makes the app faster and improves user experience.

Solution

1. Step 1: Understand the goal of performance tuning

   Performance tuning aims to make apps run faster and smoother for users.

2. Step 2: Identify the effect on user experience

   A faster app improves how users feel and interact with it, making it more enjoyable.

3. Final Answer:

   It makes the app faster and improves user experience. -> Option D

4. Quick Check:

   Performance tuning = better speed and experience [OK]

Hint: Performance tuning improves speed and user experience [OK]

Common Mistakes:

• Thinking it adds new features automatically
• Believing it changes framework size
• Assuming it affects app colors

2. Which Angular feature helps improve performance by reducing change detection checks?

easy

A. Using inline styles

B. Adding more components

C. Using the OnPush change detection strategy

D. Increasing the number of services

Solution

1. Step 1: Identify Angular features for performance

   OnPush strategy tells Angular to check components only when inputs change, reducing work.

2. Step 2: Compare other options

   Adding components or services does not reduce checks; inline styles affect appearance only.

3. Final Answer:

   Using the OnPush change detection strategy -> Option C

4. Quick Check:

   OnPush reduces checks = better performance [OK]

Hint: OnPush reduces unnecessary checks in Angular [OK]

Common Mistakes:

• Confusing inline styles with performance tuning
• Thinking more components improve speed
• Believing more services reduce checks

3. What will be the effect of lazy loading a feature module in Angular?

medium

A. The app loads faster initially by loading modules only when needed.

B. The app loads all modules at once, slowing startup.

C. The app disables routing for the lazy loaded module.

D. The app increases bundle size unnecessarily.

Solution

1. Step 1: Understand lazy loading in Angular

   Lazy loading delays loading a module until the user navigates to it, reducing initial load time.

2. Step 2: Analyze other options

   Loading all modules at once slows startup; disabling routing or increasing bundle size are incorrect effects.

3. Final Answer:

   The app loads faster initially by loading modules only when needed. -> Option A

4. Quick Check:

   Lazy loading = faster initial load [OK]

Hint: Lazy loading delays module load until needed [OK]

Common Mistakes:

• Thinking lazy loading loads all modules upfront
• Assuming routing is disabled
• Believing bundle size grows unnecessarily

4. Given this Angular code snippet, what is the main performance issue?

  @Component({
    selector: 'app-list',
    template: `
      

        {{ item.name }}
      
    `,
    changeDetection: ChangeDetectionStrategy.Default
  })
  export class ListComponent {
    @Input() items: any[] = [];
  }

medium

A. Using Default change detection causes unnecessary checks on every change.

B. The *ngFor directive is not allowed in Angular templates.

C. The component is missing a selector.

D. The items input should be a string, not an array.

Solution

1. Step 1: Identify change detection strategy

   The component uses Default strategy, which runs checks on all changes, even if items don't change.

2. Step 2: Understand impact on performance

   This causes Angular to check the component often, slowing performance especially with large lists.

3. Final Answer:

   Using Default change detection causes unnecessary checks on every change. -> Option A

4. Quick Check:

   Default strategy = more checks, slower performance [OK]

Hint: Default change detection runs often, slowing app [OK]

Common Mistakes:

• Thinking *ngFor is invalid syntax
• Missing the selector is not the issue here
• Assuming input type is wrong

5. You want to improve an Angular app's performance by minimizing change detection and loading only needed code. Which combination is best?

hard

A. Use OnPush change detection and load all modules eagerly.

B. Use OnPush change detection and lazy load feature modules.

C. Use Default change detection and load all modules eagerly.

D. Use Default change detection and lazy load feature modules.

Solution

1. Step 1: Choose change detection strategy

   OnPush reduces unnecessary checks by running only when inputs change, improving speed.

2. Step 2: Choose module loading strategy

   Lazy loading delays loading modules until needed, reducing initial load time and memory use.

3. Step 3: Combine strategies for best performance

   Using both OnPush and lazy loading together maximizes performance benefits.

4. Final Answer:

   Use OnPush change detection and lazy load feature modules. -> Option B

5. Quick Check:

   OnPush + lazy loading = best performance [OK]

Hint: Combine OnPush and lazy loading for best speed [OK]

Common Mistakes:

• Using Default detection reduces speed
• Loading all modules eagerly slows startup
• Mixing strategies reduces benefits