title: How to display on HTML page load a function's return?
body: <p>I'm trying to display some information on an HTML web page when the viewer loads the web page. I have a function, called getID(email), that returns an integer. I know that this works, as I've tested with console and it works properly. My issue is being able to display the return of getID() onto the web page when the page loads.</p>
  
  <p>I know that I have to use <code>document.getElementById('div id goes here').innerHTML('content goes here');</code> to change what a div says,  but for the life of me I can't get the actual information.</p>
  
  <p>Here's what I have:</p>
  
  <pre><code>&lt;div id='output'&gt;
  
  &lt;/div&gt;
  
  &lt;script&gt;
  function showId() {
    var id = google.script.run.getId(Session.getActiveUser().getEmail());
    document.getElementById('output').innerHTML(id);
  &lt;/script&gt;
  </code></pre>
  
  <p>I have no idea how to make this run when the HTML page is loaded. Help is appreciated!</p>