Promises.js

const aPromise = new Promise((resolve, reject) => {
   setTimeout(() => {
      if(true) {
         resolve('I am here!');
      } else {
         reject('No! It is an error!');
      }
   }, 5000)
})

// single promises handle
aPromiseWithData(false)
  .then((data) => {
     console.log(data);
  })
  .catch((err) => {
     console.log(err);
   })

// multiple promises handle
Promise.all([promise1, promise2]).then((dataArr) => {
   console.log(dataArr);
})

// using fetch api
fetch('https://jsonplaceholder.typicode.com/posts')
   .then((data) => {
      return data.json();
   }).then((posts) => {
      console.log(posts);
})