Query firebase from functions with express to filter item by a alphanumerical child value.

ChainQueryUsingPromises.js

/*
CHAIN MULTIPLE QUERIES USING PROMISES IN FIREBASE REALTIMEDB 
FROM EXPRESS IN FIREBASE FUNCTIONS
*/
ss.post("/test", (request,response) => {

	//Get data
	let shakes = request.body.shakes
	let uid = request.body.uid

	//The array to chain promises
	let promises = [];
	//Load coupons and gifts/
	promises.push(db.ref('/gifts').orderByChild("active").equalTo("true").once('value'));
	promises.push(db.ref('/coupons').orderByChild("active").equalTo("true").once('value'));
	//Load users current data (todays count from timestamp, gifts, vouchers)
	promises.push(db.ref('/shakes_user/' + uid).once('value'));
	//Load users current gift_allowed status. (If false, user can't anymore gifts)
	promises.push(db.ref('/shakes_user/' + uid + "/gift_allowed").once('value'));

	

	// Wait for all promises to resolve
	Promise.all(promises).then(function(res) {        
	    // res[0] is gifts.
	    // res[1] is coupons.
	    // res[2] is current users data
	    // res[3] is current users gift_allowed status
	    

	 	let gifts = res[0]; //gift
	 	let coupons = res[1]; //coupon
	 	let user_data = res[2];
	 	let gift_allowed = res[3];

	 	//Array for merging both gift and coupons
	 	let merged = [];
		
		

		//Add gifts to the array only if the gift_allowed is true
		if (gift_allowed) {
			//Loop through gift and push items to the array.
			gifts.forEach(function(item){
				merged.push(item); 	        
			})				
			response.send("worked").end();
		}
	 	
	 	//Loop through coupons and push items to the array.
	 	coupons.forEach(function(item){
	 		merged.push(item); 	        
	 	})

	 	//Get random value from the available coupons/gifts.  	 	
		var random = merged[Math.floor(Math.random() * merged.length)]; 	
		response.send(random);
	});
});

db.json

[ {
  "expires" : "1541901660",
  "id" : "gift123",
  "gift" : {
    "description" : "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce non nisi blandit, tincidunt dui ut, facilisis diam.",
    "img" : "gift.png",
    "name" : "Gift Name"
  },
  "terms" : "Lorem ipsum dolor.",
  "type" : "gift"
}, {
  "expires" : "1541901660",
  "id" : "honda_activa_1",
  "gift" : {
    "description" : "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce non nisi blandit, tincidunt dui ut, facilisis diam.",
    
    "img" : "gift.png",
    "name" : "Honda Activa"
  },
  "terms" : "Lorem ipsum dolor.",
  "type" : "gift"
}, {
  "expires" : "1541901660",
  "id" : "ipad_2018",
  "gift" : {
    "description" : "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce non nisi blandit, tincidunt dui ut, facilisis diam.",
    
    "img" : "gift.png",
    "name" : "Ipad Pro"
  },
  "terms" : "Lorem ipsum dolor.",
  "type" : "gift"
}, {
  "expires" : "1541901660",
  "id" : "ipad_2018",
  "gift" : {
    "description" : "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce non nisi blandit, tincidunt dui ut, facilisis diam.",    
    "img" : "gift.png",
    "name" : "Macbook Pro 15"
  },
  "terms" : "Lorem ipsum dolor.",
  "type" : "gift"
} ]

FirebaseFromFunctions.js

/*
ACCESS FIREBASE REALTIMEDB FROM FIREBASE FUNCTIONS
USING EXPRESS.JS
*/
const express = require("express")
var functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);

ss.get("/gift", (request, response) => {
    admin.database().ref('gifts').orderByChild('id').equalTo("gift123").once('child_added').then(snapshot => {
      //console.log(snapshot.val())
      response.send(snapshot.val())
     })
})

const api = functions.https.onRequest(ss)
module.exports = {
  api
}

load_by_id.js

/*
LOAD A ITEM IN FIREBASE REALTIMEDB USING AN ID STORED IN
IT AS CHILD.
*/

//Get gift_id from post
let gift_id = request.body.gift_id    

//Get from firebase by the gift_id 
db.ref("gifts").orderByChild("id").equalTo(gift_id).once("value",snapshot => {
     //Check if data is returned
     if (snapshot.exists()){          
       response.send(snapshot.val())		     
     } else {
       response.send("Gift id " + gift_id + "doesn't exist.")		    	
     }
});

How it looks in firebase:

Postman screenshot of the API in action: