Firebase AngularJS array map() - angularjs

Question

I have multiple firebase items that I am looping through and they have name, categoryId, lat, lon.
I am trying to calculate a distance from 2 lat,lon (one is the one in firebase), the other is the user's location.
All of this is fine, and I can calculate it fine too. However, how do I inject/map the new variable into the firebase array that I am subscribed to?
this.categoryId = this.navParams.get('categoryId');
afoDatabase.list('/list', {query: {
orderByChild: "categoryId",
equalTo: parseInt(this.categoryId)
}}).subscribe(listItems => {
this.items = listItems; //need to add distance within array
loadingPopup.dismiss().catch(() => {});
});
For example, I have a variable called distance, that calculates everything and has the value. How do I add it in the this?items - so I can call it from the HTML side?
Thanks for the help :)

Answer 1

To inject, first create a function and create a variable (e.g. this.distance) and get the value of your function on this variable. After that use a for loop to increment, based on length - and use this.items[i]["distance"] to add to each one. For example:
this.categoryId = this.navParams.get('categoryId');
afoDatabase.list('/list', {query: {
orderByChild: "categoryId",
equalTo: parseInt(this.categoryId)
}}).subscribe(listItems => {
this.items = listItems;
this.geolocation.getCurrentPosition({timeout:15000}).then((resp) => {
this.myLat = resp.coords.latitude;
this.myLong = resp.coords.longitude;
}).catch((error) => {
console.log('Error getting location', error);
});
for (var i = 0, len = this.items.length; i < len; i++) {
this.distance = this.calculateDistance(this.myLat, this.myLong, this.items[i].lat, this.items[i].lng);
this.items[i]["distance"] = Math.round(this.distance);
console.log('testing myLat', this.myLat)
console.log('testing myLong', this.myLong)
}
console.log('testing inject', this.items)
loadingPopup.dismiss().catch(() => {});
});
Function
calculateDistance(lat1:number,lon1:number,lat2:number,lon2:number){
let R = 6371; // km
let dLat = (lat2 - lat1) * Math.PI / 180;
let dLon = (lon2 - lon1) * Math.PI / 180;
let a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
Math.cos(lat1 * Math.PI / 180) * Math.cos(lat2 * Math.PI / 180) *
Math.sin(dLon / 2) * Math.sin(dLon / 2);
let c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
let d = R * c;
return d;
}