How To Return Data From JavaScript Promise

In this tutorial, you’ll learn how to return data from JavaScript Promise. Assuming that you have a basic understanding about JavaScript Promises, I’ll start by creating a method which returns a Promise, so that you can see how to return data from promise.

function getPromise(){
  return new Promise(function(resolve,reject){
    setTimeout(function(){
      resolve({'country' : 'INDIA'});
    },2000)
  })
}

The above method returns a promise which when resolved produces a JSON object. Let’s make a call to the above method and return its result.

function getPromise() {
    return new Promise(function(resolve, reject) {
        setTimeout(function() {
            resolve({
                'country': 'INDIA'
            });
        }, 2000)
    })
}

function getResult() {
    getPromise()
        .then(function(response) {
            return response;
        })
}

let result = getResult();
console.log(result);

As seen in the above code, getResult methods makes a call to the getPromise method and once resolved it returns the response. If you try running the above code, the result logged will be undefined. This happens because after making a call to getResult method, it in turns calls the getPromise method which gets resolved only after 2000 ms. getResult method doesn’t wait since it doesn’t returns a promise.

So, if you return a promise from getResult method it can then be used to wait for the Promise to get resolved. Let’s try it.

function getResult() {
    return getPromise()
        .then(function(response) {
            return response;
        })
}

getResult()
    .then(function(result) {
        console.log(result);
    })

Now you are able to return data from JavaScript promise.

Return Data From Promise using ES6 Async/Await

JavaScript ES6 provides a new feature called async/await which can used as an alternative to Promise.then. Using async/await you can write the above code in synchronous manner without any .then.

function getPromise(){
  return new Promise(function(resolve,reject){
    setTimeout(function(){
      resolve({'country' : 'INDIA'});
    },2000)
  })
}

async function getResult(){
  let result = await getPromise();
  return result
}

async function doTask(){
  let data = await getResult();
  console.log(data)
}
doTask();