title: ionic\angular 2: string does not updated after settimeout
body: <p>I'm trying to update a string (of a class\tag) with settimeout (or any other callback), with no success, It's working perfectly with a button (when the user is clicking the button to update), but it doesn't work with JS settimeout.
  can you tell me what am I missing here?</p>
  
  <p><strong>Here is a sample of the code I have:</strong></p>
  
  <pre><code>export class Page1 {
    constructor() {
  this.greet = "Hi, ";
  setTimeout(function(){
    this.greet = "Hello, ";
    alert("Done");
   }, 3000);
    }
  }
  </code></pre>
  
  <p>as you can see in this simple code, I can see the alert "Done" after 3 seconds, but the greeting is not updated, should I refresh it somehow?</p>
  
  <p>Thanks for helping!</p>
  
  <p>Eran.</p>