title: Block submit of a form without using JQuery and with input type="submit"
body: <p>I want to block the submit of a form in this condition:</p>
  
  <p>1) Without JQuery;</p>
  
  <p>2) With an input type="submit" (instead of type="button"), because it's the only way (i think) to submit form with Enter Key</p>
  
  <p>Here's my code:</p>
  
  <pre><code>&lt;form name="form_ricerca" action="trova_hotels.htm" id="top_form_ricerca" method="post"&gt;        
     &lt;fieldset style="margin: 10px;text-align: center;"&gt;
       &lt;input id="top_ric_strutt" type="text" name="ricerca" size="40"
       &lt;input onclick="return top_controlla_ricerca();" &gt;
     &lt;/fieldset&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>and this is the function:</p>
  
  <pre><code>function top_controlla_ricerca() {
    var nome_codice = document.getElementById("top_ric_strutt").value;
    SOME_CODE
    if (SOME_CONDITIONS) {
     document.getElementById("top_form_ricerca").submit();
     return true;
    } else {
     alert('MY_ALERT');
     return false;
    }
  }
  </code></pre>