This is due to the fact that your element is dynamically created. You should use event delegation to handle the event.
document.addEventListener('click',function(e){
if(e.target && e.target.id== 'brnPrepend'){
//do something
}
});
jquery makes it easier:
$(document).on('click','#btnPrepend',function(){//do something})
Here is an article about event delegation event delegation article