Promise Js: Wait till promise fulfilled [duplicate]

Question

I'm working with Bluebird for promises in Node.Js, and was wondering how can I make a function return when the promise is fulfilled(completed).The behavior I want is :

function getItem(){
  functionReturningPromise.then(function(result){
    //do some operation on result
    return result;
  });
}

However, the above implementation won't return anything since the promise isn't completed at the time of execution. What would be the best workaround around this?

The purpose of getItem is to modify whatever functionReturningPromise returns, and then return it

Answer 1

You can't, var value = someAsyncFunction() is not possible (until we have generators, at least). Promises are viral, once you use a Promise in a function, its caller must use then and the caller of the caller too, etc up to your main program. So, in the function that calls getItem you have to change this

item = getItem();
do something with item

into this

getItem().then(function(item) {
    do something with item
})

and getItem should return a Promise as well

function getItem(){
  return functionReturningPromise().then(function(result){
    //do some operation on result
    return result;
  });
}

(Theoretically it can also be a callback, but I prefer to always return promises).