title: Jquery Ajax and Json : How to check if undefined
body: <p>I got this Jquery code : </p>
  
  <pre><code>$.ajax({
      url: "?module=gestionApplication&amp;action=getTests&amp;scenario="+encodeURI(scenario)+"&amp;application="+$application,
      dataType:'json',
      success: function( data ) {
          $.each(data, function(i, item) {
              $("#tests tbody").append($tr+"&lt;td title='"+item.DESCRIPTION+"'&gt;"+item.ID+"&lt;/td&gt;" +
              "&lt;td&gt;"+
                  "Header : "+item.HEADER + '&lt;br/&gt;' +
                  "Méthode : "+item.METHODE +  '&lt;br/&gt;' +
                  "PostBody : "+item.POSTBODY +  '&lt;br/&gt;' +
                  "URL : "+item.URL +  '&lt;br/&gt;' +
                  "ParseReponse : "+item.PARSEREPONSE +  '&lt;br/&gt;' +
              "&lt;/td&gt;" +
  </code></pre>
  
  <p>So i got a JSON response from my server, but not all fields are full. Sometimes item.HEADER or item.METHODE can not be defined, so I get "undefined" text in my table. Problem is, I'm French and I would like different text and not this 'undefined'. </p>
  
  <p>So how can I test if the variable is defined or not? Or even better, is it possible to change this 'undefined' text to different text in case the variable is not defined?</p>