bootstrap set active tab javascript

$(document).ready(function(){
    activaTab('aaa');
});

function activaTab(tab){
    $('.nav-tabs a[href="#' + tab + '"]').tab('show');
};

 $('.nav-tabs a').on('shown.bs.tab', function(event){
  var x = $(event.target).text();         // active tab
  var y = $(event.relatedTarget).text();  // previous tab
});