title: Firestore: Multiple conditional where clauses
body: <p>For example I have dynamic filter for my list of books where I can set specific color, authors and categories.
  This filter can set multiple colors at once and multiple categories.</p>
  
  <pre><code>   Book &gt; Red, Blue &gt; Adventure, Detective.
  </code></pre>
  
  <p>How can I add "where" conditionally?</p>
  
  <pre><code>  firebase
      .firestore()
      .collection("book")
      .where("category", "==", )
      .where("color", "==", )
      .where("author", "==", )
  
      .orderBy("date")
      .get()
      .then(querySnapshot =&gt; {...
  </code></pre>