If you want to add your javascript to Joomla! header from your component, you can do it like this:

JHTML::_('behavior.mootools');
 $doc =& JFactory::getDocument();
$js = "

function show(options)
{
$('update').innerHTML = '<div align=".'"center"'."><img src="/.'"images/ajax-loader.gif" width="66" height="66"/>'."<p/>Prosim poÄŤakajte</div>'
var ajaxRequest = new Ajax('index.php', {
method: 'get',
 onComplete: function(response) {
  $('update').innerHTML = response;
  }
  });
  ajaxRequest.request(options);
 }

 window.addEvent('domready', function()
 {
 $('form1').addEvent('submit', function(e)
  {  $('update').innerHTML = '<div align=".'"center"'."><img src="/.'"images/ajax-loader.gif" width="66" height="66"/>'."<p/>Prosim poÄŤakajte</div>'
  // Stop the form from submitting
  new Event(e).stop();
  // Update the page
  this.send({ update: $('update') });
  });
  });";
  $doc->addScriptDeclaration($js);

Javascript in component you can add only once, if you try to do it twice, one javascript will be overwriten with another.