title: Uncaught ReferenceError for Javascript using onchange method
body: <p>So yesteday it was working but now it gives me error and I have no idea why..
  Here is the code i'm using:</p>
  
  <pre><code>&lt;select onchange="tipus(this);"&gt;
  
              &lt;option value="true"&gt;Heti tevékenység&lt;/option&gt;
              &lt;option value="false"&gt;Idoszakos tevékenység&lt;/option&gt;
  &lt;/select&gt;
  
              &lt;div id="ifYes" style="display: block;"&gt;
              &lt;label class="submit" for="tipus"&gt;Orák száma&lt;/label&gt; &lt;input type="number" name="orak" min="1" max="99" /&gt;&lt;br /&gt;
              &lt;/div&gt;
              &lt;div id="ifNo" style="display: none;"&gt;
              &lt;label class="submit" for="napok"&gt;Napok száma:&lt;/label&gt; &lt;input type="number" name="napok" min="1" max="99" /&gt;&lt;br /&gt;
              &lt;label  class="submit" for="car"&gt;Kezdeti dátum&lt;/label&gt; &lt;input type="date" id="datum" name="datum" /&gt;&lt;br /&gt;
              &lt;/div&gt;
              &lt;script&gt;
              function yesnoCheck(that) {
                  if (that.value == "true") {
                      document.getElementById("ifNo").style.display = "none";
                      document.getElementById("ifYes").style.display = "block";
  
                  }
                  else 
                  {
                      document.getElementById("ifYes").style.display = "none";
                      document.getElementById("ifNo").style.display = "block";
                  }
              }
              &lt;/script&gt;
  </code></pre>