can't access firebase database snapshot values outside promises

Question

I can't access snapshot value outside promises. I have these functions

function getAuthorData() {
  metadataRef
    .child("author")
    .on("value", (snap) => {
      return snap.val()
    })
}

function getSiteSocialLinks() {
  metadataRef
    .child("social")
    .on('value', (snap) => {
      return snap.val();
    })
}

function getFeaturedPosts() {
  featuredRef.on('value', (snap) => {
    return snap.val();
  })
}

function getBlogPosts() {
  blogPostsRef
  .orderByChild('createOn')
  .on('value', (snap) => {
    return snap.val()
  });
}

function getPostCategories() {
  postRef
  .child('categoryStats')
  .on('value', (snap) => {
    return snap.val();
  });
}

function getTotalPostsLength() {
  postRef
  .child('nopp')
  .on('value', (snap) => {
    return snap.val();
  })
}

and when I try this

var ourPosts = getBlogPosts()
  var ourCategories = getPostCategories()
  var totalnumOfPosts = getTotalPostsLength()

  console.log(`Our post: ${ourPosts}\n our categories: ${ourCategories}\n total number of posts: ${totalnumOfPosts}\n`)

this is what I get

Our post: undefined our categories: undefined total number of posts: undefined

I dont really know if it has anything to do with scope. Please help

asynchronous code will mess you up like that every single time — Jaromanda X, Jul 02 '17 at 23:46
use promises as they are meant to be used, perhaps? As your functions don't return anything, it's a bit difficult — Jaromanda X, Jul 02 '17 at 23:54
I have log their values inside them one by one and they all log their values correctly — Jalasem, Jul 02 '17 at 23:57
exactly, because asynchronous code is asynchronous and your functions don't return **anything**, so of course those vars inside `ourPosts` will always be undefined ... start by **returning** those "promises" (if indeed they are promises) from `getPostCategories` etc then use Promise.all, perhaps, to "wait for and get the resolved value of" those promises — Jaromanda X, Jul 03 '17 at 00:00

Broda Noel · Accepted Answer · 2017-07-03T01:48:16.370

You are not using Promises as you should.

Try this:

getBlogPosts().then(value => {
  console.log(value);
});

getPostCategories().then(value => {
  console.log(value);
});

getTotalPostsLength().then(value => {
  console.log(value);
});

And add a return before each metadataRef, something like:

function getAuthorData() {
  return metadataRef
    .child("author")
    .on("value", (snap) => {
      return snap.val()
    })
}

function getSiteSocialLinks() {
  return metadataRef
    .child("social")
    .on('value', (snap) => {
      return snap.val();
    })
}

function getFeaturedPosts() {
  return featuredRef.on('value', (snap) => {
    return snap.val();
  })
}

function getBlogPosts() {
  return blogPostsRef
  .orderByChild('createOn')
  .on('value', (snap) => {
    return snap.val()
  });
}

function getPostCategories() {
  return postRef
  .child('categoryStats')
  .on('value', (snap) => {
    return snap.val();
  });
}

You may need to read a little bit about "why promises exists", so you'll understand why you need to use it in this way.

can't access firebase database snapshot values outside promises

1 Answers1