title: Property 'from' does not exist on type 'typeof Observable'.ts(2339)
body: <p>The following code should have the result:</p>
  
  <p>4 </p>
  
  <p>16 </p>
  
  <p>Done！</p>
  
  <p>However, the VSC told me that : <code>Property 'from' does not exist on type 'typeof Observable'.ts(2339)</code></p>
  
  <p>I have no idea how to fix the problem. Could anyone help me please?</p>
  
  <p>/<em>These code should be put into any component.ts file, then npm run start to see the result in the console.</em>/</p>
  
  <pre><code>import { Observable } from 'rxjs'; 
  
  constructor() {
  
      Observable.from([1,2,3,4]).filter(e =&gt; e%2==0) 
        .map( e =&gt; e*e) 
        .subscribe( e =&gt; console.log(e),
         error =&gt; console.error(error), 
         () =&gt; console.log("Done！") 
       ) 
  }
  </code></pre>