// gotoLongestLine.jsee
if (document.selection.IsEmpty) {
  var begLine = 1;
  var endLine = document.GetLines();
}
else {
  var begLine = document.selection.GetTopPointY(eePosLogical);
  var endLine = document.selection.GetBottomPointY(eePosLogical);
}

var line = 0;
var maxLen = 0;
for (var n = begLine; n <= endLine; n++) {
  var len = document.GetLine(n).length;
  if (len > maxLen) {
    line = n;
    maxLen = len;
  }
}

if ((line > 0) && (maxLen> 0))
  document.selection.SetActivePoint(eePosLogical, maxLen + 1, line, false);