If you try running the above code, the result logged will be undefined. The argument is a function providing two arguments: a resolve and . When the first .then method returns a value, the next .then method can receive that. If the new Promise resolves, then two will also resolve by taking the new Promise 's resolved value as its own. Viewed 3k times -1 I have have array with three pet names. Promise then(.) Use of setTimeout () function: In order to wait for a promise to finish before returning the variable, the function can be set with setTimeout (), so that the function waits for a few milliseconds. It may be either fulfilled or rejected for example, resolving a rejected promise will still result in a rejected promise. archy-bold commented on Sep 6. Therefore, the correct way to get an array of promises is as follows: This makes the promise created by thenresolve with the value undefined. Click an available time slot on the calendar below to reserve a room. I have logged the output to the console in ListFile () so I know the data is correct. Promise.resolve (value) None of the above worked and in my case the problem was that I was adding a mock in a __mocks__ directory next to the file, but the import used a 'scoped module'. If a promise has succeeded or failed and you later add a success/failure callback, the correct callback will be called, even though the event took place earlier. If you return a Promise, the resolution of this two determined by the fate of this new Promise. always return 'undefined' Node. Promise is returning undefined. Mar 16, 2022 P Paulie Guest Mar 16, 2022 #1 Paulie Asks: Firebase Promise Returning Undefined Data Javascript I've followed several guides on how to correctly wait for the data from my ListFile () function. If you still want to use promises, that's fine. A JavaScript Promise object can be: Pending; Fulfilled; Rejected; The Promise object supports two properties: state and result. to see whether the rejected promise is caught. Answer 1. :P. Thanks in advance for your help! This means you will get undefined as the return value of apiGetAll. I'm trying to get a value back from this promise but it keeps returning undefined on my template.If you look at my getLabel function, I am getting the label in the argument which is a promise. When a Promise object is "fulfilled", the result is a value. Use of async or await () function. Promise is replaced with callbacks, etc. Runs without error in IE11. For instance, in the code below the URL to fetch is wrong (no such site) and .catch handles the error: My recommendation is to restructure the code to use promises throughout. When a Promise is created, it will be pending. Target is to fetch pets from api and if pet not exist to return altered array with only existing pet names. And we can not access the real output when it is available using the Promise return by the 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 with return countQuery.then (.). So instead of: var list = _getById({ groupId: 42}); console.log("Our list is: "+list); You'll: fmarsella February 15, 2021, 1:57pm #1. If a function returns a Promise, it means that the result of the function call is not available. 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 cannot succeed or fail twice, neither can it switch from success to failure or vice versa. But how can I use .then () to get and use the response in the vue file. // create an array of items from obj const items = Object.keys (obj); // turn it to an array of promises for database queries A promise represents the eventual result of an asynchronous operation. How to return data from promise; Export Cookie Jar to JSON with Node Request; node.js call external exe and wait for output; node.js resolve promise and return value; How can I send an object to a file, process that object, return and get the result because I'm missing something here and I do not understand why I get undefined and my Promise . If it rejects, it is rejected with the reason from the first promise that was rejected. If the returned promise fulfills, it is fulfilled with the value of the first promise in the iterable that fulfilled. Problem is that Promise.all() return undefined. W3Guides. It does return a promise but does not have the ability to convert callback based functions to Promises that can be used with await. You get a promise of a result. When a Promise object is "rejected", the result is an . Instead of "get the id, then do something with it", you need to "do something whenever the id is loaded/changed". 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. I think I know why, because I return the Axios within an async function. function fetchIDs {. To do that there is two popular way described below. Your title asks why new Promise is returning undefined, when the fact is that it isn't. It is indeed returning a valid promise. A promise can only succeed or fail once. Use of setTimeout () function. There are a number of copies of this issue floating around and most of them are labeled as a dupe of #4260 , however on cursory glance of that issue I think perhaps the reality is that #4260 is a a prerequisite before fixing this issue. Your test function does return a undefined. The documentation mentions it. Fails in IE 11 with error SCRIPT5009: 'Promise' is undefined. 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. Stack Overflow - Where Developers Learn, Share, & Build Careers Ask Question Asked 3 years, 11 months ago. I am resolving it and returning it to my title in my . Description The static Promise.resolve function returns a Promise that is resolved. Try it Syntax Promise.all(iterable) Parameters iterable An iterable (such as an Array) of promises. When a promise rejects, the control jumps to the closest rejection handler. stopAll () { startmeetingApi.stop ().then ( (res) => { this.transcript = res.data.transcript; }); console.log (this.transcript . If we are now returning anything inside two, TypeScript will replace the previous Hey with an undefined. While a Promise object is "pending" (working), the result is undefined. For that you need to use the original Promise constructor. edited to join this conversation on GitHub . Promise.all(promises) .then(objects => { var music = objects[0] console.log("music", objects[0]) // This prints out "music undefined" profile.music = music } The weird thing is when I print out the iTunes api result that I'm returning in the promise, it prints fine. However, in the promise completion block it's always undefined. code to use result .}) - Jaromanda X Jun 22, 2017 at 6:36 In Example 2, the getGithubOrgs(url) function calls the Fetch API, which returns a Promise that resolves to a response object. Only works in IE 11 if bluebird.min.js script element is uncommented. If not let mw know! It allows us to call the next .then method on the new promise. From Node Lecture Asynchronous JavaScript : 8- Consuming Promises Hello Forum, I'm confused why the third then( ) always return undefined. One is incorrect. Because promisedDivision (n1, 0) now would return rejected promises, let's also wrap the invocation into a try {. } Modified 3 years, 11 months ago. remove the promise.then null function, and finally, realise that var result = fileExists ("url_to_file"); will mean result is a Promise - if you want to wait for the promise to fulfill you'll need to do result.then (function (result) { . Advanced Search Only show rooms with the following amenities: 65" J-Touch: HDMI Wired Connectivity Possible: Local PC 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. The reason it is returning undefined is because get_message () is not returning anything. So const api will always equal undefined. Promise Object Properties. But async/await would have made it clearer that you have to set state in the the callback because the value doesn't exist until the promise returns. The catch() method returns a Promise and deals with rejected cases only. The primary way of interacting with a promise is through its then method, which registers callbacks to receive either a promise's eventual value or the reason why the promise cannot be fulfilled. Promise.all() return undefined. Cleaner, simpler. 1 People found this is helpful async-await javascript node.js Advertisement When calling a function that returns a promise, comes back as undefined unless async operators are removed, then returns ZoneAwarePromise, but contains no data. replace countQuery.then (.) Share Follow answered Aug 18, 2015 at 6:49 Matt Way 31.4k 10 77 83 4 Thanks Matt - your suggested change makes it work as expected. That's very convenient in practice. JavaScript - Cannot read property 'then' of undefined. Return value A Promise that is resolved with the given value, or the promise passed as value, if the value was a promise object. I had to add a folder for the scoped module under the root mocks folder ie __mocks__/@module/file.js. throws an error, the promise returned by then gets rejected with the thrown error as its value. If you added, say, return 'finished'; to the end of get_message (), then your var a would end up having the value 'finished' instead of undefined. Promise resolver undefined is not a function at new Promise (<anonymous>) The fix is straightforward: you must provide a way to resolve or reject promises: // Instead of this const promise = new Promise() // do this const promise = new Promise(() => {}) That will fix the problem. It is just that resolve is not a valid function on the promise object. You will need to use the promise to get access to the offers. The promise.then() call always returns a promise. Answers related to "return undefined on async method js" async function javascript promise async async function javascript dec javascript return data async javascript await return value javascript make async get request .then (async async await catch reject async function in variable Async return values Get async: false js undici fetch data async Your code proceeds . Blockquote You'll have to change the way you code. This promise will have the state as pending and result as undefined. You want to do it prior (but there's more, keep reading): let throttleAsync = function(url) { return promise.then(() => { catch (error) {.} getId Cannot read property 'then' of undefined . It rejects when any of the input's promises rejects, with this first rejection reason. returns an already fulfilled promise, the promise returned by then gets fulfilled with that promise's value as its value. Examples angularjs; javascript; angular-promise; 2022-07-27 11:25. Already have an account? It behaves the same as calling Promise.prototype.then(undefined, onRejected) (in fact, calling obj.catch(onRejected) internally calls obj.then(undefined, onRejected)). You cannot return data that is being loaded asynchronously. export function getHotOffers () { let offerPromise = getRequest ('/hot-offers') .then (offers => JSON.parse (offers)); return offerPromise; } Similarly, any code that calls this will be getting a promise and will have to use its .then method to get the final value. This means that you have to provide an onRejected function even if you want to fall back to an undefined result value - for example obj.catch(() => {}). If you want a promise of an optional that is fine, but your T should be T|undefined in this case. Home Web Design Programming Languages Database Design and Development Software Development Tools Artificial Intelligence Mobile Development Computer Science. In some cases, you may want to check the status of the promise. Finally, then() returns a new Promise that resolves to JSON. You need to return a promise for the result: function test(p) { return Promise.all(ccxt.exchanges.map(api => { //Looping . A promise can be one of the three states below. Promise.reject (reason) Returns a new Promise object that is rejected with the given reason. This resulting Promise is received by the then() method, which parses the response to JSON using the json() method. But whenever I use it, it always says that .then () is undefined. Your estimation () function returns undefined instead of returning a promise, that is because you return the new string from the callback function. 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. To make the function promisedDivision (n1, n2) return a rejected promise let's set the second argument to 0. change var promise = to return . Why is Promise.all returning the array without waiting on the requests'results? Promise.resolve(r) fetchIDs (GET ). Just return the promise directly. The first state is called the Pending state. 8 People found this is helpful async-await javascript promise reactjs Advertisement The second one can now pass to the third .then() and so on. doesn't return anything, the promise returned by then gets resolved with an undefined value. As an async function, readThatSHIT wraps the empty return value (undefined) in a promise and returns that. to be compatible with ES5. When calling a function that returns a promise, comes back as undefined unless async operators are removed, then returns ZoneAwarePromise, but contains no data. I hope that was clear enough! You probably meant to have it return the new promise you're creating, but you're not doing that until the setTimeoutcallback. Angular 5 Promise returns undefined, Angular service returning undefined to component, Angular 2 - Http with promise return Undefined, Angular observable return undefined results. The JavaScript language Promises, async/await June 18, 2022 Error handling with promises Promise chains are great at error handling. How can I use.then ( ) return undefined viewed 3k times -1 I have have array with existing! 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