function switchVisible(checkedAll){
     if(checkedAll){
        selectAllLabel.hide();
        deselectAllLabel.show();
     }else{
        selectAllLabel.show();
        deselectAllLabel.hide();
     }
}
$('.selectAll').change(function(e){
   langs.map(function(d){
       this.checked = selectAll.is(':checked');
       switchVisible(this.checked);
   });
});
deselectAllLabel.click(function(e){
   langs.map(function(d){
       this.checked = false;
       switchVisible(true);
   });
});
invertSelect.click(function(e){
   langs.map(function(d){
       this.checked = !this.checked;
       langs.change();
   });
});
langs.change(function(d){
    var num = langs.filter(':checked').length;
    switchVisible(num === langs.length);
    selectAll.prop('checked',num === langs.length);
 });