MDN: Checking that the fetch was successful I'm doing an async/await addition function, using a given promise-creating function which should take 100ms before being called. Let's pretend you are building a book app and you want to fetch a book with its author and ratings. 5 When calling a function that returns a promise, comes back as undefined unless async operators are removed, then returns ZoneAwarePromise, but contains no data. Asynchronous code is "infectious", if you want to wait for a promise in a function, then that function itself will have to become awaitable, e.g. Nope. Async/Await with Request-Promise returns Undefined This is using a REST endpoint to pull data, the console.logs do show the data is correct, however return comes back as undefined this.allPeople.forEach (async person => { const dodString = await this.getRelatedRecords (person); //undefined } This is the main function that returns a promise / data follow. 13. you're currently immediately resolving your outer promise but with an inner promise, and that inner promise doesn't return anything at all, hence undefined. Async/Await returns undefined. The count ().exec methods returning a Promise, I'm trying to resolve it in order to return the value to the user. If the promise passed to the handle function resolves it returns [data, undefined]; If it was rejected, the handle function still resolves it and returns [undefined, Error] Similar solutions Easier Error Handling Using Async/Await - Jesse Warden NPM Package - await-to-js Conclusion grepper; search ; writeups; faq; docs ; install grepper 12. } I know the query returns data when the function executes, it however does not seem to pass that data to the actual return part of the function call. If you're defining a function with asynchronous behavior, you can use async/await or Promise chaining. We will solve this issue in three ways: Using Callback functions Using Promise Using Async/Await Using Callback Function We will use Callback functions to read multiple files and print their respective content/data. then ( data => { console . log ( data ) // 3, not a promise wrapping the . Try it Syntax Promise.all(iterable) Parameters iterable An iterable (such as an Array) of promises. I'm trying to return the count from my database. Returning Description All async functions wrap their return value in a promise. 8 People found this is helpful. . Vue.nextTick() returns a Promise, of which you are awaiting.The awaited value is undefined, which is also correct. Use of async and await enables the use of ordinary try / catch blocks around asynchronous code. ASYNC AWAIT RETURN UNDEFINED; javascript async await values undefined; async function returning undefined; await return undefined; await function returns undefined; await promise returns undefined; async returning undefined; js await function returns undefined; javascript undefined response await; nodejs async await return undefined; node await . with return countQuery.then (.). I can't figure it out. You can also see how the AI plays against the AI. await expression Parameters expression A Promise, a thenable object, or any value to wait for. In the future, we will be able to use await outside of async functions, but you typically need one these days. app.js Async/Await in Axios. Just return the promise directly. The solution is pretty simple. If you want the promise to have a value, then do resolve (someValue). You're calling an async request within this function, so the function will never be able to return the result of this async request synchronously. This returned promise fulfills when all of the input's promises fulfill (including when an empty iterable is passed), with an array of the fulfillment values. It rejects immediately upon any of the input promises rejecting or non-promises throwing an error, and will reject with this first rejection message / error. log ( response . When a Promise object is "rejected", the result is an error object. I have looked at several Stack questions that have not answered this question including this question: Async/Await with Request-Promise returns Undefined This is using a REST endpoint to pull data, the console.logs do show the data is correct, however return comes back as undefined 4 1 this.allPeople.forEach(async person => { 2 Looks to me to be an async issue. then ( response => { console . Javascript let firstPromise = () => { by returning a promise, or by being declared as "async function ()", and then inside "await"-ing the promise. const delayedPromise = ms =&gt; new Promise(resolve =&gt; setTimeout( We have written various tests for the application. In most situations, especially if the promises successfully resolve, there isn't a big difference between using return await promise and return promise. While a Promise object is "pending" (working), the result is undefined. E.g. You can check whether a method supports promises by checking its API reference page: The example method, captureVisibleTab (), can be found in the chrome.tabs API. reject() method returns a Promise object that is rejected with a given reason. Fetch API The Promise returned from fetch () won't reject on HTTP error status even if the response is an HTTP 404 or 500. await db.promisePool.getConnection() - return promise await conn.execute - return idk what, coz it's working sometimes(for example 2 queries on same connection, without any caching on mysql server) without await too, just returning nothing, empty array, that's strange. When we make a promise in real life, it is a guarantee that we will do something in the future because promises can only be made for the future. Here, if you call foo, the returned promise will always wait one second, then either fulfill with undefined, or fulfill with "caught".. Because we await the result of waitAndMaybeReject(), its rejection will be turned into a throw, and our catch block will execute.However, if waitAndMaybeReject() fulfills, we don't do anything with the value.. When the await keyword is used in a function, the next line of the function is not ran before the promise has been resolved or rejected. Await expressions make promise-returning functions behave as though they're synchronous by suspending execution until the returned promise is fulfilled or rejected. Inside an async function, you can use await or chain .then () to wait for asynchronous responses. Promise lets asynchronous methods return values like synchronous methods: instead of immediately returning the final value, the asynchronous method returns a promise to supply the value at some point in the future. 1. save input fields to Collection 1 2. query Collection 1 for product id to retrieve ID 3. save input fields to Collection 2 including ID (retrieved in step 2) to create the reference link between collection 1 & 2 The results of the query in step 2 sometimes returns the id and sometimes return undefined. Personally, I don't see why you're resolving in complete at all. It rejects when any of the input's promises rejects, with this first rejection reason. By definition, resolve () in your complete handler will set the resolved value in the returned promise to undefined. It's not shown in your code where you are actually invoking the replace method, but this function is being called too soon. You don't know when, but you will be able to detect it (then or await). Wherever you're calling this function you'll need to use the resulting promise to handle the result. When a promise returns data, that data will never be a promise itself. However, if you want to catch the rejected promise you're returning from an asynchronous function, then you should definitely use return await promise expression and add deliberately the await. Async/Await. In this article, we have written an AI for Tic-Tac-Toe. A Promise is in one of these states: With the command line interface, you can play this game against the AI or another human. Advertisement. Answer 1. This helped me get the value from an async/await axios called. JavaScript Promise. Answers related to "await returns undefined" javascript undefined is undefined false in javascript Subscription field must return Async Iterable. If you try running the above code, the result logged will be undefined. The ESLint rule no-return-await disallows the use of return await inside an async function. When the line returns a promise. ~ MDN. if the data returned from a promise would also be a promise then it will wait for that promise as well. Fulfilled Rejected The Promise object supports two properties: state and result. The main thing to note at this point is that it has an operator co_await() method that returns an, as yet, undefined type, awaiter. Without an async/await, the data variable may come back undefined, since it may not fetch the response from the API before the return executes. To understand await then, we need to understand promises. You are calling a MongoDB methods before you have connected to the MongoDB cluster in your main method. You have learned how Minimax works for turn-based games. Async/Await with Request-Promise returns Undefined - NodeJS [ Glasses to protect eyes while coding : https://amzn.to/3N1ISWI ] Async/Await with Request-Prom. A function invoked with await will always resolve the promise and return the resolved value. It seems to me I have well used the async / await methodology, so what is wrong ? Instead, it will resolve normally (with ok status set to false), and it will only reject on network failure or if anything prevented the request from completing. This method supports promises because one of the method's signatures returns a promise. Asynchronous functions are prefixed with the async keyword; await suspends the execution until an asynchronous function return promise is fulfilled and unwraps the value from the Promise returned.,TypeScript 1.7 adds ES6 to the list of options available for the --module flag and allows you to specify the module output when targeting ES6. Promise. Return value The fulfillment value of the promise or thenable object, or the expression itself's value if it's not thenable. conn.unprepare(query); return obj with/without await Even though our async function seemingly returns a number, it actually returns a promise. To make this easier to see at a glance, the reference docs also display a Promise pill below . Answers related to "javascript async await returns undefined" try catch async await async await iife javascript promise async javascript return data async AsyncStorage.getItem undefined is not an object javascript await return value javascript make async get request .then (async javascript async await not waiting async function in variable When we invoke a function that returns a promise, we chain the then() method of the promise to run a function when the promise resolves. Exceptions Throws the rejection reason if the promise or thenable object is rejected. replace countQuery.then (.) 1 People found this is helpful async-await javascript node.js Advertisement If the promise type, P, has a member named await_transform then <expr> is first passed into a call to promise.await_transform(<expr>) to obtain the Awaitable value, . function ask (text) { return new Promise ( (res, rej) => { @Tatiana_Wiener - Thank you so much for the additional information and context - it's so helpful!. Author: Ahmed Bouchefra Follow @ahmedbouchefra Your original Fiddle adheres to this. new Promise ( resolve => { resolve ( new Promise ( innerResolve => innerResolve ( 3 ) ) } ) . The await keyword in the snippet above does what it describes: it forces the rest of the code to literally await the promise until it resolves. That is the standard interaction between Promises and async/await. Async makes it so that the function always returns a promise. async-await javascript promise reactjs. 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. We still get a Promise object. Await. In this article, I will show you how to use Promise.all () along with array destructuring. Using new JavaScript syntax you can drastically improve the readability and performance of your code. The proposal for the language feature has currently made it to stage 3 and is hoping to go to the final stage 4 by November of 2019. It says: Since the return value of an async function is always wrapped in Promise.resolve, return await doesn't actually do anything except add extra time before the overarching Promise resolves or rejects. When a Promise object is "fulfilled", the result is a value. We get undefined data from all of the files we are trying to read because of the asynchronous nature of Node.js code. Await is the keyword we use when we want to wait for a line to finish, but it only works in certain situations: In an async function. [Solved]-NodeJS - Promise returns undefined object inside a redis pool await-node.js score:0 Accepted answer in your attempts you use await configPool.get ('allImages', async (err, reply) => { firstly, .get doesn't return a promise, so await ing it makes no sense secondly, you're not using await inside the callback, so no need to make it async For some bizarre reason, the TypeScript docs don't explain how to implement type checking for Promises, Async/Await, or Generator Functions.. status ) }) Your function returns a Promise with the resolved value or error to its callers. Basically, the return type of the Promise is defined immediate after the Promise keyword. Here's an example using the Fetch API : fetch ( '/data.json' ) . 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