Promises

Promises.js

const ourPromise = new Promise((resolve, reject) => {
    setTimeout(() => resolve('Hello'), 1000)
});

ourPromise
.then(resolvedValue => {
    return resolvedValue;
})
.then(anotherValue => {
    return new Promise((resolve, reject) => {
        Math.random() > 0.5 ?
            setTimeout(() => resolve('Hello'), 10000) :

            setTimeout(() => reject(new Error('Bye')), 10000)
    })
})

new Promise(resolve => {
    document.addEventListener('click', resolve);
})

const request = fetch('/api/user').then(response => response.json());

renderWhenLoaded(request);

function renderWhenLoaded(request) {
    request.then(user => {
        const {
            firstName,
            lastName,
            links
        } = user;

        const result = {
            fullName: `${firstName} ${lastName}`
        }
        const linksPromises = links.map(({ social_network, id }) =>
            getSocialNetworkUrl(social_network, id)
        );

        return Promise.all(linksPromises).then(links => {
            return {
                ...result,
                links
            }
        })
    })
}