How to make some text in text area bold?

Hi All,

Following is the code I used to make some part of text in text area Bold.

new sap.ui.commons.TextArea({

    cols : 43,

  rows : 4,

  visible : true,

  enabled : false,

  value: { parts:[

              {path: 'uidata>loggedInUserName'},

              {path: 'uidata>commentDate'},

              {path: 'uidata>loggedInUserComments'}

                ],

     formatter: function(caseId,custNo,title) {

      var boldc=caseId.bold();

         return boldc+" --- "+custNo.bold()+"\n"+title;

         return caseId+" --- "+custNo+"\n\n"+title;

      }

  },

  })

It didn't work. Can anyone help?

Thanks in advance