View source for Basic Hints

== Basic Hints  ==

Questionnaire viewer is implemented in a way that you can add javascript to manipulate the way your questions are displayed. 

jQuery is already included in the viewer, thanks to&nbsp;what&nbsp;javascript has even more powerful effect! (read more about jquery here:&nbsp;[http://jquery.com/ http://jquery.com/]) 

Javascript is a property on both question and questionnaire levels, which means that you can add javascript for each question or for the whole questionnaire. 

The most important features are: 

*quest: the current question's object 
*questioncheck: the function called before going Next

=== quest  ===

Some important properties of quest object: 

*quest.questions:&nbsp;array of sub questions 
*quest.options: array of answer options

Methods of quest object: 

*quest.setQuestions(Array subQuestions): assign an array of question objects to the sub question list of the current question 
*quest.setOptions(Array options): assign an array of options to the answer option list of the current question 
*quest.setAnswer(string value): assign a value to the question 
*quest.getHTML(): returns the HTML which will be rendered to display the question 
*quest.onInit(): called right after loading the question 
*quest.rotateAnswerOptions(startIndex, endIndex, rotateIndex): rotate answer options in a range specified by startIndex and endIndex, the first item in the range will be rotateIndex 
*quest.rotateSubQuestions(startIndex, endIndex, rotateIndex):&nbsp;rotate sub questions in a range specified by startIndex and endIndex, the first item in the range will be rotateIndex 
*quest.randomizeAnswerOptions(randomSeed, startIndex, endIndex):&nbsp;randomize answer options in a range specified by startIndex and endIndex, the order&nbsp;is unique&nbsp;for each randomSeed 
*quest.randomizeSubQuestions(randomSeed, startIndex, endIndex):randomize sub questions in a range specified by startIndex and endIndex, the order is unique for each randomSeed<br>

=== questioncheck()  ===

We need to override this function to get rid of the default question check supported by the questionnaire viewer, it is a must when showing more than one questions in the same page. The function returns true when there is nothing wrong and false otherwise. 

There is an object which should be used to display errors: ErrorMessages. 

*ErrorMessages.getInstance().clearErrorMessages(): clear all existing error messages 
*ErrorMessages.getInstance().showErrorMessage(msg): show an error message

If you want to extend the questioncheck function with special cases then you should re-create the questioncheck function carefully, because else you will create an endless loop. If you get a stack overflow error from the browser, then your problem should be solved by the following script pattern: 

<source lang="javascript">// Store a reference to the default question check
var defaultQuestionCheck = questioncheck;

// Implement your own question check routine
var questioncheck = function()
{
   // Call the default question check
   // If it fails
   if (!defaultQuestionCheck())
      // Then return at once with false
      return false;
      
   // Catch exceptions, this is just for precaution
   try
   {
      // Optimistic assumption that everything is OK
      var valid = true;

      // Do your customized question checks here set variable
      // valid to false if the question is answered incorrectly

      if (!valid)
      {
         // You might want to clear default error messages given
         ErrorMessages.getInstance().clearErrorMessages();

         // Add your own error message
         ErrorMessages.getInstance().showErrorMessage("An error message");

         // Terminate the question check by returning false
         return false;
      }
   }
   catch(e)
   {
      // Inform about the reason for the exception
      alert(e.message);

      // And return false
      return false;
   }

   // Everything is OK      
   return true;
}</source> 

== Technical tips ==

=== Include an external script library ===

In case we want to use external javascript libraries hosted on external servers (like google), we need to include the library link to quest.onInit.<br/>A simple method of doing so is using jquery's getScript method ([http://docs.jquery.com/Ajax/jQuery.getScript#urlcallback http://docs.jquery.com/Ajax/jQuery.getScript#urlcallback])

'''Example:'''<br/><source lang="javascript">
$.getScript("http://ui.jquery.com/testing/ui/ui.datepicker.js", function()
 {
 //the library is now ready to use
 }
);
</source>

Do not include a js library as an attachment in a question's script, otherwise you will have a problem with resource access when respondents view the questionnaire.<br/>'''Solution for this''': if the script is short, copy it and put directly into the question/questionnaire's script, if it is big, find an external host (ex: google host).<br/>If you still wants to go with attachment, then create a new group with observer access to the attachments, add a dummy question in the questionnaire to add the current user to the group automatically, also add anonymous user to the group.