Validate SharePoint people picker before Save.

Scenario: When user enters firstName LastName in people picker and click SharePoint save, without validating user.
Site shows error message

Reason : We have 30,000+ user and 5+ domains so request time-outs.

Fix : Ask user to validate people picker before save.

JavaScript :

function getPickerInputElement(identifier)
{
    var tags = document.getElementsByTagName('DIV');
    for (var i=0; i < tags.length; i++)
    {    
        var tempString = tags[i].id;        
        if ((tempString.indexOf('UserField_upLevelDiv') > 0))
        {
            if(identifier == tempString)
            {
                var innerSpans = tags[i].getElementsByTagName("SPAN");  
                for(var j=0; j < innerSpans.length; j++)
                {
                    if(innerSpans[j].id == 'content')
                    {
                        return innerSpans[j].innerHTML;
                    }
                }
            }  
        }
    }
    return "";
}

/* SharePoint 2010 calls below function on save click */
function PreSaveAction()
{
   var returnValue = true;
   var requestorPerson = getPickerInputElement('<DIV ID OF PEOPLE PICKER>');
   if(!requestorPerson || requestorPerson == "")
   {
     returnValue = false;
     alert(' <FIELD> is not validated. Please validate.\n Enter "Email Address" or "Domain\LANID" and click validate button next to text box.');

   }
   return returnValue
}
/******************** END OF JAVA SCRIPT ******************/