Promise.js

// returns collection with identifer `id`
const getStrings = () => {
    return new Promise((resolve) => {
        resolve([
            {
                id: "id",
                sourceString: "{1} word"
            }
        ])
    });
}
// accepts an array of ids, returns collection
const getPlaceholders = (stringIds) => {
    return new Promise((resolve) => {
        resolve(stringIds.map(id => ({id, placeholders: []})))
    });
}
// accepts array of ids, returns collection
const getKeys = (stringIds) => {
    return new Promise((resolve) => {
        resolve(stringIds.map(id => ({id, key: "key"})))
    });
}
// returns { strings, placeholders, keys }
// get strings first, than using their ids make requests to keys and placeholders (parallely of course)
// return all three collections in one object
// if getKeys gets rejected still return resolved promise with { strings, placeholders, keys: [] }
const getStringData = () => {
    return new Promise((resolve) => {
        getStrings().then((strings) => {
            resolve(strings);
        })
    })
    .then((strings) => {
        return getPlaceholders(strings)
        .then(getKeys(strings))
    })
    .then((strings, placeholders, keys) => {
        return Promise.resolve({ strings, placeholders, keys });
    })
}
// task is to implement getStringData as described above, current implementaion is not correct
// can be done with Promises or async/await syntax