toolbar : show some

attaching error.
do i need to use window. ?

<FlexmonsterReact.Pivot ref="pivot" toolbar = "true"
beforetoolbarcreated = {this.customizeToolbar()}
 
customizeToolbar(toolbar) {
// get all tabs.
var tabs = toolbar.getTabs();
console.log("tabs" + tabs);
toolbar.getTabs = function () {
// delete the first tab
delete tabs[0];
return tabs;
}
}
 

got below error
TypeError: Cannot read property ‘getTabs’ of undefined

i tried some documentation. am good now.