Promises in Javascript ES6

promises_es6.js

// Snippet for Promises (ES6)

// Create a Promise that is resolved and handle it using "then" methods
let p = new Promise( (resolve, reject) => {
  setTimeout( () => {
    resolve("Good to go!");
  }, 1000);
});

p.then( 
  (data) => {
    console.log(data);
  },
  (err) => {
    console.log(err);
  }
);

// Create a Promise that is rejected and handle it using "then" and "catch" methods
// Here we can see that, even if we have a resolve and a reject, if the promise
// has already changed to a "resolved" or "rejected" state it cannot change
// its state any more. That's why we only see the rejected value.
let p2 = new Promise( (resolve, reject) => {
  setTimeout( () => {
    resolve("Good to go!");
  }, 1000);
  
  setTimeout( () => {
    reject("Oops that didn't go well...");
  }, 500);
});

p2.then( (data) => {
    console.log(data);
}).catch( (err) => {
    console.log(err);
});

// Handle the resolved state of several promises
Promise.all([p, p2])
    .then( (data) => {
        console.log(data);
    })
    .catch( (err) => {
        console.log(err);
    });

// Visit https://promisesaplus.com/ for more information