title: Rxjs switchMap not calling the function passed through it
body: <p>I'm using <code>Subject</code> observable from <code>rxjs</code>. I've two methods that I called from my component.</p>
  <ol>
  <li>Search</li>
  </ol>
  <pre class="lang-typescript prettyprint-override"><code>search(terms: Observable&lt;string&gt;) {
    return terms.pipe(
      debounceTime(400),
      distinctUntilChanged(),
      switchMap(term =&gt; {
        this.numberOfItems = API_INFO.PER_PAGE_ITEMS;
        return this.getPosts(term)
      })
    );
  }
  </code></pre>
  <ol start="2">
  <li>Loadmore</li>
  </ol>
  <pre class="lang-typescript prettyprint-override"><code>loadmore(terms: Observable&lt;string&gt;, pageNumber) {
    this.numberOfItems = API_INFO.PER_PAGE_ITEMS * pageNumber;
    return terms.pipe(
      debounceTime(0),
      switchMap((term: string) =&gt; this.getPosts(term))
    )
  }
  </code></pre>
  <p>component subscription code</p>
  <pre class="lang-typescript prettyprint-override"><code>this.homeService.search(this.searchLocation$)
        .subscribe((data)=&gt;this.handleSuccess(data),(err)=&gt;this.handleError(err))
  </code></pre>
  <p>The issue is <code>search</code> works fine while <code>loadmore</code> doesn't although they both have the same code</p>
  <p>PS: I'm using the same subscription model for both of the observable</p>