title: How to get TypeScript to recognize firebase import
body: <p>I am trying to show content from firestore in a small TypeScript web application by accessing firestore client-side. However, tsc is failing to compile as it cannot find the firebase module.</p>
  
  <p>In the head of my index.html, I have imported the firebase-app.js from gstatic, firebase-firestore.js from gstatic, as well as my compiled script.js in that order. I currently have 3 TypeScript files compiling to the single js file and I am trying to load the data in the first of three files.</p>
  
  <p>My index.html imports the three scripts in the head here</p>
  
  <pre class="lang-html prettyprint-override"><code>    &lt;script src="https://www.gstatic.com/firebasejs/6.1.1/firebase-app.js"&gt;&lt;/script&gt;
  
      &lt;script src="https://www.gstatic.com/firebasejs/6.1.1/firebase-firestore.js"&gt;&lt;/script&gt;
  
      &lt;script src="scripts/script.js" type="module"&gt;&lt;/script&gt;
  </code></pre>
  
  <p>Then my tsconfig.json compiles the three files using these options</p>
  
  <pre><code>{
      "compilerOptions": {
          "target": "esnext",
          "watch": true,
          "outFile": "public/scripts/script.js",
          "module": "system"
      },
      "files": [  
                  "scripts/temp.ts",
                  "scripts/loaddata.ts",
                  "scripts/control.ts"
              ]
  }
  
  </code></pre>
  
  <p>Finally, the first line of temp.ts is where the error occurs when I do my imports</p>
  
  <pre><code>import * as firebase from 'firebase/app';
  import 'firebase/firestore';
  
  const firebaseConfig = {
  //config here
  }
  
  firebase.initializeApp(firebaseConfig);
  
  let db = firebase.firestore();
  </code></pre>
  
  <p>VS Code is giving me the syntax error Cannot find module 'firebase/app' and thus fails to compile. I have tried several different combinations of firebase and app and have been unsuccessful in importing the module. Is it possible to compile multiple TypeScript files into a single javascript file while using firebase/firestore? I was successfully able to retrieve my data using raw JavaScript but I would prefer to use TypeScript as that is what the rest of my project is written in!</p>