Ionic 2: Add new array into array of objects - arrays

Question

I would like to add an array into an array object. However, I am only able to add the array into a new object instead of the existing one. Is there any way where I can link the array to the existing object? Its much more easier for me too if I could add in the array based on which link it is from.
Here is my code:
this.af.database.list(`/users/${userid}/favourites`, {
query: { orderByChild: 'priority' },
preserveSnapshot: true
})
.subscribe(snapshots => {
snapshots.forEach(snapshot => {
this.category.push({
name: snapshot.val().name,
rss: snapshot.val().regions[0].rss
});
})
for (let i = 0; i < this.category.length; i++) {
this.http.get(this.category[i].rss)
.map(res => res.text())
.subscribe((data) => {
this.parseXML(data)
.then((data) => {
this.xmlItemsApac = data
this.category.push({
feeds: data
})
});
});
}
});
console.log(this.category)
parseXML(data) {
return new Promise(resolve => {
var k,
arr = [],
parser = new xml2js.Parser(
{
explicitArray: false
});
parser.parseString(data, function (err, result) {
var obj = result.rss.channel;
for (k in obj.item) {
var item = obj.item[k];
arr.push({
title: item.title,
link: item.link,
description: item.description,
pubDate: item.pubDate
});
}
resolve(arr);
});
});
}