Observable rxjs filter

Question

In my project, I wanted to create some sort of "Recommended Products" in each product page, but having trouble with making my function filtering an observable.

I have tried using .pipe(filter()) in different ways, but to no use.

Basically the fucntion should filter products with the same type and id , and show them in the proper product page, but pretty much got stuck after subscribing all of my products(which is marked down below).

Much Appreciated!

 import { Component, OnInit } from '@angular/core'; import { ProductService } from '../services/product.service'; import { ActivatedRoute, ParamMap, Router } from '@angular/router'; import Product from '../interfaces/product'; import { map, filter} from 'rxjs/operators'; import { Observable } from 'rxjs'; @Component({ selector: 'app-product', templateUrl: './product.component.html', styleUrls: ['./product.component.css'] }) export class ProductComponent implements OnInit { recommandedProducts: Product[]; allProducts:Product[]; // allProducts:Observable< Product> = new Observable< Product>(); product: Product; constructor(private productService: ProductService, private route: Router, private actRoute: ActivatedRoute) { } ngOnInit() { this.findRecommendedProducts(this.product) }; //From ProductService: // getProducts(){ // return this.http.get(`${this.uri}`); // } findRecommendedProducts(currectProduct: Product){ this.productService.getProducts().subscribe((data: Product[]) => { this.allProducts = data; console.log(this.allProducts) this.recommandedProducts = this.allProducts.filter(otherProduct => otherProduct.type == currectProduct.type && otherProduct.id == currectProduct.id) console.log(this.recommandedProducts); }); }; }

Answer 1

A filter in rxjs is not the same as an Array.filter . In rxjs, a filter is used to emit values that pass the provided condition. So if you use a filter, based on the condition, the observable will either emit your data or return nothing.

Instead, what you need is pipe(map) along with an Array.filter . Also, as @jzzfs pointed out, your error shows currentProduct could be undefined , so you can pass a default value in your findRecommendedProducts function.

Try the below code.

findRecommendedProducts(currectProduct: Product = {} as Product) {
    this.productService.getProducts()
    .pipe(
        map((products: Product[]) => products.filter(product => product.type == currectProduct.type && product.id == currectProduct.id))
    )
    .subscribe((data: Product[]) => {
        this.recommandedProducts = data;
    });      
};

Now your subscribed data should directly return the recommendedProducts .

Answer 2

Looks like the currectProduct passed onto findRecommendedProducts is undefined , since the logged this.allProducts do contain values.

With that being said, notice that when you define product: Product , you've only defined its type but you have not initialized it. The default value is therefore undefined -- if I remember correctly.

So change product: Product to product: Product = {}; , for instance or pass a value to it within the constructor or within ngInit .