How can i return something from a function like this?

Question

I'm quite new to typescript and have a fuction that will fetch user's steam inventory and store it in "inventory" parameter, but when i want to return it it will return undefined:

function getUserInv(steamid) {
    manager.getUserInventoryContents(steamid, 440, 2, true, function(err, inventory) {
        if(err) {
            console.log(err);
        } else {
            return inventory
        };
    });
};

console.log(getUserInv('<my steamid>')) //returns undefined

How can i make it so that when i call it like above, it returns the inventory?

score 4 · Accepted Answer · answered Jun 16 '22 at 07:11

you can wrap it into a Promise like this

function getUserInv(steamid) {
    return new Promise((resolve, reject) => {
    manager.getUserInventoryContents(steamid, 440, 2, true, function(err, inventory) {
        if(err) {
            reject(err);
        } else {
            resolve(inventory)
        };
    });
}
};

getUserInv('<my steamid>').then(console.log)

score 1 · Answer 2 · answered Jun 16 '22 at 07:14

Because this function returns a value asynchronously, you need to return a data type that can handle asynchronous values.

In JS, that is called a promise. You can access their value by registering a callback using .then(), or in TypeScript and other modern JS environments, you can use the nice async/await syntax.

Here is how you would create and return a promise from your function.

function getUserInv(steamid: string): Promise<Inventory> {
  return new Promise((resolve, reject) {
    manager.getUserInventoryContents(steamid, 440, 2, true, function(err, inventory) {
        if(err) {
            reject(err);
        } else {
            resolve(inventory);
        };
    });
  });
}

// Using .then():
getUserInv('<my steamid>').then(inv => console.log(inv));

// Using async/await:
console.log(await getUserInv('<my steamid>'));

How can i return something from a function like this?

2 Answers2