import { Injectable } from '@angular/core';
import { Meta } from '@angular/platform-browser';
import { Title } from '@angular/platform-browser';
@Injectable()
export class SeoService {
private titleService: Title;
private metaDescriprtion: Meta
constructor(
    private _meta: Meta,
    private _titleService: Title
) {}
public setTitle(newTitle: string) {
    this._titleService.setTitle(newTitle);
}
public setMetaDescription(description: string) {
    this._meta.addTag({name: "description", content: description})
}
}
Above code does't show title and description in view-source.