es6-promise

问题 I have the following code. And it works as expected without throwing a unhandled rejection error. p = new Promise (fulfill, reject) -> reject new Error 'some error' p.catch (error) -> console.log error Now, the second code example does throw an unhandled rejection error. Can someone explain to me why this is happening when im clearly handling the error. p = new Promise (fulfill, reject) -> reject new Error 'some error' p.then -> console.log 'ok' p.catch (error) -> console.log error Btw. I'm

问题 The difference between Code#1 and Code#2 is: Code#1 uses resolve(p) and Code#2 uses p.then(()=>resolve()) . I would expect the sequence of output to be invariant, but they generate a different sequence. I cannot figure out why. Code #1: resolve(p) const p = Promise.resolve(); new Promise((resolve) => { resolve(p); // <--- }).then(() => { console.log('after:await'); }); p.then(() => console.log('tick:a')) .then(() => console.log('tick:b')) .then(() => console.log('tick:c')); Output: tick:a

问题 The difference between Code#1 and Code#2 is: Code#1 uses resolve(p) and Code#2 uses p.then(()=>resolve()) . I would expect the sequence of output to be invariant, but they generate a different sequence. I cannot figure out why. Code #1: resolve(p) const p = Promise.resolve(); new Promise((resolve) => { resolve(p); // <--- }).then(() => { console.log('after:await'); }); p.then(() => console.log('tick:a')) .then(() => console.log('tick:b')) .then(() => console.log('tick:c')); Output: tick:a

问题 I am able to successfully perform a Promise.all, and gracefully handle resolves and rejects. However, some promises complete within a few milliseconds, some can/could take a while. I want to be able to set a timeout for each promise within the Promise.all, so it can attempt to take a maximum of say 5seconds. getData() { var that = this; var tableUrls = ['http://table-one.com','http://table-two.com']; var spoonUrls = ['http://spoon-one.com','http://spoon-two.com']; var tablePromises = that

问题 So i have been playing with promises for the last few days, and just trying to convert some project, to use promises, but more than a few times i have encuntered this issue. While reading articles and tutorials everything looks smooth and clean: getDataFromDB() .then(makeCalculatons) .then(getDataFromDB) .then(serveToClient) But in reality, its not like that. Programs have a lot of "if conditions" that changes the whole flow: getDataFromCache(data).then(function(result){ if(result){ return

问题 This question already has answers here : Wait until all promises complete even if some rejected (17 answers) Closed 3 years ago . Am I misunderstanding Promise.all? I have X promises in an array and i'm trying to aggregate the success/failure ratio of the array. Here is what I think I know: Promise.all takes an array of promises. If all of the promises succeed then the .then callback is ran. If one of the promises fail then the .catch callback is called and the argument passed in is the value

问题 So I am learning Angular 2 with typescript. I am reaching a point to write a mocking service which (I believe) should return a Promise if the service get the Object Successfully and Return an Error if anything happens. I have tried following code but looks like it is not a write syntax for typescript. Updated the CODE: saveMyClass(updatedMyClass: MyClass){ //saving MyClass using http service //return the saved MyClass or error var savedMyClass : MyClass = someLogicThatReturnsTheSavedObject

问题 I try to give out a general solution for retrying a promise. Below is my way and comes an error of "Uncaught (in promise)". How can I fix this problem? function tryAtMost(maxRetries, promise) { let tries = maxRetries return new Promise(function(resolve, reject) { promise.then((result) => { resolve(result) }) .catch(err => { if (tries > 0) { console.log(`tries with ${tries}`) tryAtMost(--tries, promise); } else { reject(err) } }) }) } tryAtMost(3, promise).then(result => { console.log(result)

问题 I'm trying to make an asynchronous loop with native ES6 promises It kind of works, but incorrectly. I suppose I made a huge mistake somewhere and I need someone to tell me where it is and how it's done correctly var i = 0; //creates sample resolver function payloadGenerator(){ return function(resolve) { setTimeout(function(){ i++; resolve(); }, 300) } } // creates resolver that fulfills the promise if condition is false, otherwise rejects the promise. // Used only for routing purpose function

问题 I am running a forEach loop on an array and making two calls which return promises, and I want to populate an object say this.options , and then do other stuff with it. Right now I am running into the async issue if i use the following code sample and i get into the then function first. $.when.apply($, someArray.map(function(item) { return $.ajax({...}).then(function(data){...}); })).then(function() { // all ajax calls done now }); This is working code below, but it only works for the first