JavaScript Promises, road to async/await - https://codingblast.com/javascript-promise-async-await

PromisesAsyncAwait.js

function someFunction(value, error) {
  return new Promise((resolve, reject) => {
    if (value) {
      resolve(13);
    } else {
      reject(error);
    }
  });
}

function fetchPost(id) {
  return fetch('https://jsonplaceholder.typicode.com/posts/' + id)
  .then(
    response => response.json(),
    error => error)
  .then(function(post) {
    return post;
  });
}

async function mainFunction() {
  try {
    let id = await someFunction('Some value');
    let post = await fetchPost(id);
    console.log(post);
  } catch (error) {
    console.error(error);
  }
}

mainFunction();