***Update:  This code does not work in Firefox***

 

I'll start this post with a disclamer that this code is not my own, I found different parts of the following code in different blog posts around the internet, but could not find this complete solution in one coherent post, so I decided to put it up myself.  I found the beginning of the code here.

 

Place the following code just inside the PlaceHolderMain tag of a newform.aspx page, or on a page with any custom form on it, and it should automatically populate a people or groups field with the name of the currently logged on user.

 

<script type="text/javascript">
_spBodyOnLoadFunctionNames.push("fillDefaultValues");

 

function fillDefaultValues() {

  var qs = location.search.substring(1, location.search.length);

  var args = qs.split("&");

  var vals = new Object(getUserDisplayName());
 
  var assignedToInput = getTagFromIdentifierAndTitle("div", "", "People Picker");

  assignedToInput.innerHTML = vals;

  for (var i=0; i < args.length; i++) {

    var nameVal = args[i].split("=");

    var temp = unescape(nameVal[1]).split('+');

    nameVal[1] = temp.join(' ');

    vals[nameVal[0]] = nameVal[1];

  } 
}
 

function getTagFromIdentifierAndTitle(tagName, identifier, title) {

  var len = identifier.length;

  var tags = document.getElementsByTagName(tagName);

  for (var i=0; i < tags.length; i++) {

    var tempString = tags[i].id;

    if (tags[i].title == title && (identifier == "" || tempString.indexOf(identifier) == tempString.length - len)) {

      return tags[i];

    }

  }

  return null;

}
function getUserDisplayName() {

 var tags = document.getElementsByTagName('a');

 for (var i=0; i < tags.length; i++) {

  if(tags[i].innerText.substr(0,7) == 'Welcome') {

   return tags[i].innerText.substr(8,tags[i].innerText.length);

  }

 }

}
</script>