title: Extracting the input value from a mathjax paper-input polymer object
body: <p>I am trying to read the value the user inputs into a polymer paper-input object. However, this is a custom object as follows :</p>
  
  <pre><code>&lt;dom-module id="mathjax-input"&gt;
  &lt;template&gt;
     &lt;paper-input  on-input="handleInputChanged" label="{{ label }}" value="{{ formula }}"&gt;
     &lt;/paper-input&gt;
  &lt;/template&gt;
  </code></pre>
  
  <p>This is intending to show the user input translated (if it's in LaTeX code) to the equivalent LaTeX result. The following is the input box:</p>
  
  <pre><code>&lt;div&gt;
  &lt;mathjax-input id="formula" label="Enter formula: " &gt;&lt;/mathjax-input&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Assuming now that the "onsubmit" event of the form calls the following function:</p>
  
  <pre><code>&lt;script&gt;
  function copy_latex(){
                  var input = document.getElementById('formula').value                  
                  return true;
                  }
  &lt;/script&gt;
  </code></pre>
  
  <p>variable "input" should now get what the user typed. This is not working though. Can you please help me locate the error? 
  -Thanks!!</p>