JAVASCRIPT

js then

doSomething()
.then(function(result) {
  return doSomethingElse(result);
})
.catch(failureCallback);

.then javascript

var doSome = new Promise(function(resolve, reject){
    resolve('I am doing something');
});

doSome.then(function(value){
    console.log(value);
});

then js

new Promise( (res, rej) => {
  setTimeout(() => res(1), 1000);
}).then( (res) => {
  console.log(res); // 1
  return res*2
}).then( (res) => {
  console.log(res); // 2
});

JavaScript then() method

promiseObject.then(onFulfilled, onRejected);

.then javascript

const promise2 = doSomething().then(successCallback, failureCallback);