Assign return value of function to variable

Question

I kind of got the same question as has been asked here.

I've made a function:

const rewardStayingViewersOrNewcomers = () => {
  fetch('https://tmi.twitch.tv/group/user/instak/chatters')
  .then(parseJSON)
  .then(r => {
    let chatters = r.chatters;
    viewerKeys = Object.keys(chatters); // [mods, viewers,...]
    let ChattersPerRole = viewerKeys.map(role => {
      return chatters[role].map(username => ({
        username, role
      }));
    });
    return flattenDeep(ChattersPerRole);
  }).catch(err => {
    console.log(`Error in fetch: ${err}`);
  });
};

Why can't I assign that return value to my variable? The log of that variable returns undefined...

let viewersPerRole = rewardStayingViewersOrNewcomers();
setTimeout(() => console.log(viewersPerRole), 7000);

Bonus question, how could I easily wait for viewersPerRole to be filled with the data I'm waiting for because of the fetch? (so I don't have to use setTimeout())?

motanelu · Accepted Answer · 2016-10-15 21:13:30Z

0

First of all, try returning something from the main function. There's no return in front on the fetch(...). Code should look like:

const rewardStayingViewersOrNewcomers = () => {
  return fetch('https://tmi.twitch.tv/group/user/instak/chatters')
  .then(parseJSON)
  .then(r => {
    let chatters = r.chatters;
    viewerKeys = Object.keys(chatters); // [mods, viewers,...]
    let ChattersPerRole = viewerKeys.map(role => {
      return chatters[role].map(username => ({
        username, role
      }));
    });
    return Promise.resolve(flattenDeep(ChattersPerRole));
  }).catch(err => {
    console.log(`Error in fetch: ${err}`);
  });
};

// now that you're returning a promise
rewardStayingViewersOrNewcomers()
  .then(viewersPerRole => console.log(viewersPerRole))

If you're using Babeljs to transpile with stage3 enabled, have a look at async / await.

edited Oct 15, 2016 at 21:13

answered Oct 15, 2016 at 21:07

motanelu

4,0251 gold badge16 silver badges21 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Kevin Over a year ago

Why do you have to put the return in front of the fetch?

motanelu Over a year ago

You need to return a value that will be the result of calling rewardStayingViewersOrNewcomers(). If you don't do that, the result will be undefined.

Kevin Over a year ago

Well, I was returning data by: return flattenDeep(ChattersPerRole);, no?

motanelu Over a year ago

That was being to the rewardStayingViewersOrNewcomers() not from. If you do let foo = fetch() ... then foo was the result of return flattenDeep(ChattersPerRole);. Not if you want to have a return value from the rewardStayingViewersOrNewcomers() function, you just need to return foo; at the end. I just cut the middle man and returned it directly.

Collectives™ on Stack Overflow

Assign return value of function to variable

1 Answer 1

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related