promises.js

const posts = [
    {
        title: 'Post One',
        body: 'This is post one'
    },
    {
        title: 'Post Two',
        body: 'This is post two'
    }
];

function getPosts() {
    setTimeout(() => {
        let output = '';
        posts.forEach((post, index) => {
            output += `<li>${post.title}</li>`;
        });
        document.body.innerHTML = output;
    }, 1000);
}

function createPost(post, callback) {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            posts.push(post);

            const error = false;
            if (!error) {
                resolve();
            } else {
                reject("Error: Something went wrong");
            }
        }, 2000);
    });
}

getPosts();
createPost({
    title: 'Post Three',
    body: 'This is post three'
}).then(getPosts);

const promise1 = Promise.resolve('Hello, World!');
const promise2 = 10;
const promise3 = new Promise((resolve, reject) => {
    setTimeout(resolve, 2000, "Goodbye, World!");
});
const promise4 = fetch('https://jsonplaceholder.typicode.com/posts/1').then(response => response.json());


Promise.all([
    promise1,
    promise2,
    promise3,
    promise4
]).then(values => {
    console.log(values);
});