http://www.howtocreate.co.uk/tutoria...ript/domevents - тут хорошо все описано.
var fireOnThis = document.getElementById('someID');
var evObj = document.createEvent('MouseEvents');
evObj.initMouseEvent( 'click', true, true, window, 1, 12, 345, 7, 220, false, false, true, false, 0, null );
fireOnThis.dispatchEvent(evObj);