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103 changes: 103 additions & 0 deletions content/components/avoid heavy computations in getters
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---
title: avoid heavy computations in getters
author:
name: Claude Assistant
url: https://github.com/claude
---

# Problem
Using getters with complex computations or transformations in components can lead to performance issues since getters are executed on every change detection cycle, even if the underlying data hasn't changed. This can cause unnecessary re-calculations and slow down the application.

# Solution
Instead of using getters for heavy computations, use regular methods or calculate values when the data actually changes (e.g., in ngOnChanges or when triggered by specific actions).

- **Bad practice**
```ts
@Component({
template: `
<div>
<h3>Product Statistics</h3>
<p>Filtered Products: {{ filteredProducts.length }}</p>
<ul>
<li *ngFor="let product of filteredProducts">
{{ product.name }} - {{ product.price }}
</li>
</ul>
</div>
`
})
export class ProductsComponent {
private _products: Product[] = [];

// Getter will run on every change detection
get filteredProducts() {
return this._products
.filter(p => p.isActive)
.sort((a, b) => b.price - a.price)
.map(p => ({
...p,
name: p.name.toUpperCase(),
price: this.calculateDiscountedPrice(p)
}));
}

private calculateDiscountedPrice(product: Product): number {
// Complex price calculation
return product.price * (1 - product.discount) * this.seasonalMultiplier;
}
}

Good practice

tsCopy@Component({
template: `
<div>
<h3>Product Statistics</h3>
<p>Filtered Products: {{ filteredProducts.length }}</p>
<ul>
<li *ngFor="let product of filteredProducts">
{{ product.name }} - {{ product.price }}
</li>
</ul>
</div>
`
})
export class ProductsComponent implements OnInit, OnChanges {
private _products: Product[] = [];
filteredProducts: ProcessedProduct[] = [];

@Input() set products(value: Product[]) {
this._products = value;
this.updateFilteredProducts();
}

ngOnInit() {
this.updateFilteredProducts();
}

ngOnChanges(changes: SimpleChanges) {
if (changes['products']) {
this.updateFilteredProducts();
}
}

private updateFilteredProducts() {
this.filteredProducts = this._products
.filter(p => p.isActive)
.sort((a, b) => b.price - a.price)
.map(p => ({
...p,
name: p.name.toUpperCase(),
price: this.calculateDiscountedPrice(p)
}));
}

private calculateDiscountedPrice(product: Product): number {
return product.price * (1 - product.discount) * this.seasonalMultiplier;
}
}
Resources

Angular Performance Best Practices
Change Detection in Angular
Using OnPush Change Detection Strategy