Dynamically add meta description based on route in

问题:

I'm using Angular 5 to build a small brochure type website. Thus far, I have my routes set up, and the page title changes dynamically based on the activated route. I got this working using the instructions on this blog: https://toddmotto.com/dynamic-page-titles-angular-2-router-events

I'm currently storing my routes and titles in app.module.ts as such:

imports: [
    BrowserModule,
    RouterModule.forRoot([
      { 
        path: '', 
        component: HomeComponent,
        data: {
          title: 'Home'
        }
      },
      { 
        path: 'about', 
        component: AboutComponent,
        data: {
          title: 'About'
        } 
      },
      { 
        path: 'products-and-services', 
        component: ProductsServicesComponent,
        data: {
          title: 'Products & Services'
        }  
      },
      { 
        path: 'world-class-laundry', 
        component: LaundryComponent,
        data: {
          title: 'World Class Laundry'
        }  
      },
      { 
        path: 'contact', 
        component: ContactComponent,
        data: {
          title: 'Contact'
        }  
      },
      { 
        path: '**', 
        component: NotFoundComponent,
        data: {
          title: 'Page Not Found'
        }  
      }
    ])
  ],

I'd like to store my meta descriptions there as well, if adding them under data: would be easy enough.

I'm pulling in that title data with the following code, which is noted in the blog link above:

ngOnInit() {
    this.router.events
      .filter((event) => event instanceof NavigationEnd)
      .map(() => this.activatedRoute)
      .map((route) => {
        while (route.firstChild) route = route.firstChild;
        return route;
      })
      .filter((route) => route.outlet === 'primary')
      .mergeMap((route) => route.data)
      .subscribe((event) => {
        this.titleService.setTitle(event['title']);
      });
  }

So my question is, is there a way to dynamically set the meta description using the same method? If there is a way to combine the page title and meta description function, that would be ideal.

I have very limited Angular training, so this might be a nooby question. I'm more of a designer/css/html kind of guy.

回答1:

First create a SEOService or Something like below:

import {Injectable} from '@angular/core'; 
import { Meta, Title } from '@angular/platform-browser';

@Injectable()
export class SEOService {
  constructor(private title: Title, private meta: Meta) { }


  updateTitle(title: string) {
    this.title.setTitle(title);
  }

  updateOgUrl(url: string) {
    this.meta.updateTag({ name: 'og:url', content: url })
  }

  updateDescription(desc: string) {
    this.meta.updateTag({ name: 'description', content: desc })
  }

After injecting the SEOService in your component, set meta tags and title in OnInit method

ngOnInit() {
this.router.events
  .filter((event) => event instanceof NavigationEnd)
  .map(() => this.activatedRoute)
  .map((route) => {
    while (route.firstChild) route = route.firstChild;
    return route;
  })
  .filter((route) => route.outlet === 'primary')
  .mergeMap((route) => route.data)
  .subscribe((event) => {
    this._seoService.updateTitle(event['title']);
    this._seoService.updateOgUrl(event['ogUrl']);
    //Updating Description tag dynamically with title
    this._seoService.updateDescription(event['title'] + event['description'])
  }); 
}

Edit: For RxJs 6+ which uses pipe operator

ngOnInit() {
    this.router.events.pipe(
       filter((event) => event instanceof NavigationEnd),
       map(() => this.activatedRoute),
       map((route) => {
         while (route.firstChild) route = route.firstChild;
         return route;
       }),
       filter((route) => route.outlet === 'primary'),
       mergeMap((route) => route.data)
      )
      .subscribe((event) => {
        this._seoService.updateTitle(event['title']);
        this._seoService.updateOgUrl(event['ogUrl']);
        //Updating Description tag dynamically with title
        this._seoService.updateDescription(event['title'] + event['description'])
      }); 
    }

Then configure your routes like

      { 
        path: 'about', 
        component: AboutComponent,
        data: {
          title: 'About',
          description:'Description Meta Tag Content',
          ogUrl: 'your og url'
        } 
      },

IMHO this is a clear way of dealing with meta tags. You can update facebook and twitter specific tags easier.

回答2:

Title and Meta are providers that were introduced in Angular 4 and supposed to do this on both server and client side.

To create or update title tag and description meta tag, it is:

import { Meta, Title } from '@angular/platform-browser';

...

constructor(public meta: Meta, public title: Title, ...) { ... }

...

this.meta.updateTag({ name: 'description', content: description }); 
this.title.setTitle(title);

回答3:

Angular 6+ and RxJS 6+ solution for dynamically set title on route change

If/when you upgrade to Angular 6 this is the solution there.

This service will:

• Update meta title on route change.
• Option to override title for any reasons you want that.

Create/change your SEO/meta service to the following.

import { Injectable } from '@angular/core';
import { Title, Meta } from '@angular/platform-browser';
import { Router, NavigationEnd, ActivatedRoute } from '@angular/router';
import { filter, map, mergeMap } from 'rxjs/operators';

@Injectable({
    providedIn: 'root'
})
export class MetaService {
    constructor(
        private titleService: Title,
        private meta: Meta,
        private router: Router,
        private activatedRoute: ActivatedRoute
    ) { }

    updateMetaInfo(content, author, category) {
        this.meta.updateTag({ name: 'description', content: content });
        this.meta.updateTag({ name: 'author', content: author });
        this.meta.updateTag({ name: 'keywords', content: category });
    }

    updateTitle(title?: string) {
        if (!title) {
            this.router.events
                .pipe(
                    filter((event) => event instanceof NavigationEnd),
                    map(() => this.activatedRoute),
                    map((route) => {
                        while (route.firstChild) { route = route.firstChild; }
                        return route;
                    }),
                    filter((route) => route.outlet === 'primary'),
                    mergeMap((route) => route.data)).subscribe((event) => {
                        this.titleService.setTitle(event['title'] + ' | Site name');
                    });
        } else {
            this.titleService.setTitle(title + ' | Site name');
        }
    }
}

Import your service and call it in the contructor.

app.component.ts

constructor(private meta: MetaService) {
    this.meta.updateTitle();
}

And this still requires to format routes like this.

Route file.ts

{ 
    path: 'about', 
    component: AboutComponent,
    data: {
      title: 'About',
      description:'Description Meta Tag Content'
    } 
  },

Hope this will help for you and other people looking to update the title/meta dynamically in Angular 6.

回答4:

Here are the relevant parts from my project. (Angular 2/4)

---

app-routing.module.ts:

Routes:

... const appRoutes: Routes = [
    {
        path: 'path1', loadChildren: './path1#path1Module',
        data: {
            title: '...',
            description: '...',
            keywords: '...'
        }
    },
    {
        path: 'path2', loadChildren: './path2#path2Module',
        data: {
            title: '...',
            description: '...',
            keywords: '...'
        }
    } ...

app.component.ts (or your bootstrap component):

imports:

// imports
import { Component, OnInit} from '@angular/core';
import { Router, ActivatedRoute, NavigationEnd } from '@angular/router';
import 'rxjs/add/operator/filter';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/mergeMap';
import { Title,Meta } from '@angular/platform-browser';

constructor:

    // constructor:
        constructor(private router: Router,
                    private route: ActivatedRoute,
                    private titleService: Title, private meta: Meta) {}

ngOnInit() method:

ngOnInit() {

        this.router.events
            .filter((event) => event instanceof NavigationEnd)
            .map(() => this.route)
            .map((route) => {
                while (route.firstChild) route = route.firstChild;
                return route;
            })
            .filter((route) => route.outlet === 'primary')
            .mergeMap((route) => route.data)
            .subscribe((event) => {
                this.updateDescription(event['description'], event['keywords'], event['title']);
            });

    }

method that updates title and meta tags -> called from ngOnInit():

updateDescription(desc: string, keywords: string, title: string) {
    this.titleService.setTitle(title);
    this.meta.updateTag({ name: 'description', content: desc })
    this.meta.updateTag({ name: 'keywords', content: keywords })
    this.meta.updateTag({ name: 'og:title', content: title })
    this.meta.updateTag({ name: 'og:description', content: desc })
}

Hope it helps.