How to add items to lightning tree component through controller?

Question

I am trying to add items to the lightning tree component through the controller js file on the click of a button. I already have all the data pulled in on the load event. What happens now is it just loads the labels expanded with no items. Here is my js code:

    loadSuitesForMDU : function(component, event, helper) {     
    var streetName = event.getSource().get("v.title");
    var city = event.getSource().get("v.name");
    var selectedMduUnits = component.get("v.mduInfoForChartAndRightContent");        
    var unitsToFilter = selectedMduUnits.filter(x => { return x.Name === streetName && x.sumchans__city__c === city; });
    var filterNn = unitsToFilter.filter(x => { return x.sumchans__accountNumber__c === undefined && x.sumchans__contactNumber__c === undefined; });
    var filterCc = unitsToFilter.filter(x => { return x.sumchans__accountNumber__c === undefined && x.sumchans__contactNumber__c != undefined; });
    var filterAa = unitsToFilter.filter(x => { return x.sumchans__status__c === 'On-billing'; });
    var items = [{
        "label": "Never",
        "expanded": true,
        "items": [filterNn]
    }, {
        "label": "Active",
        "expanded": true,
        "items": [filterAa]
    }];        
    component.set("v.suitesList",items);     

},

Here is the markup:

<lightning:tree items="{! v.suitesList }" header="Suites"/>

Answer 1

Array filter method always returns a new Array. You are assigning nested array to "items" change "items" : [filterNn] to "items" : filterNn and "items" : [filterAa] to "items" : filterAa