es6-promise

问题 I heard such an opinion that you should avoid usage of try/catch at all because it takes many resources. So could promise error handling could be faster? Or it does not matter at all? function f(somethingDangerous) { return new Promise((resolve, reject) => { // try { // somethingDangerous(); // resolve(); // } catch (err) { // reject(err); // } // VS somethingDangerous(); resolve(); }).catch((err) => { console.error('Catched: ' + err); }); } f(() => {throw 'DANGEROUS THING';}); UPD : I know

问题 I'm in the process of replacing some old code that used jQuery Deferred objects and I am rewriting using Bluebird/ES6 Promises. If I have multiple asynchronous calls, how can I trigger a function after all the promises are resolved. Using jQuery Deferreds it would be something like this: var requests = [...]; //some arbitrary data that is iterated to generate multiple ajax requests var promises = []; resuests.forEach(function(endpoint) { promises.push($.ajax({url: endpoint})); }); $.when

问题 My question is about performance in my NodeJS app... If my program run 12 iteration of 1.250.000 each = 15.000.000 iterations all together - it takes dedicated servers at Amazon the following time to process: r3.large: 2 vCPU, 6.5 ECU, 15 GB memory --> 123 minutes 4.8xlarge: 36 vCPU, 132 ECU, 60 GB memory --> 102 minutes I have some code similair to the code below... start(); start(){ for(var i=0; i<12; i++){ function2(); // Iterates over a collection - which contains data split up in

问题 If I have two promises A and B, only one of which will succeed, how can I get whichever one fulfills successfully? I'm looking for something similar to Promise.race , but which will return only the first promise that fulfills. I'm using promises from ES6. 回答1: Invert the polarity of the promises, and then you can use Promise.all , because it rejects on the first rejected promise, which after inversion corresponds to the first fulfilled promise: const invert = p => new Promise((res, rej) => p

问题 I am looking for a way, with Node v7.6 or above, to get a Bluebird Promise (or any non-native promise) when an async function is called. In the same way I can do: global.Promise = require('Bluebird'); // Or Q/When var getResolvedPromise = () => Promise.resolve('value'); getResolvedPromise .tap(...) // Bluebird method .then(...); See: May I use global.Promise=require("bluebird") I want to be able to do something like: global.Promise = require('Bluebird'); // Or Q/When var

问题 This is a follow up to this question. I have a firebase function which is supposed to take an OTP, validate it and then change a user's password based on whether it is correct or not (for some reason I'm not able to use firebase's inbuild password reset functionality). Following is my function: exports.resetPassword = functions.https.onCall((data, context) => { return new Promise((resolve, reject) => { if(data.sesId && data.otp){ admin.firestore().collection('verification').doc(data.sesId)

问题 This is a follow up to this question. I have a firebase function which is supposed to take an OTP, validate it and then change a user's password based on whether it is correct or not (for some reason I'm not able to use firebase's inbuild password reset functionality). Following is my function: exports.resetPassword = functions.https.onCall((data, context) => { return new Promise((resolve, reject) => { if(data.sesId && data.otp){ admin.firestore().collection('verification').doc(data.sesId)

问题 I found an interest thing about Promise. When I run the following codes, it gave me the output of 'aa' as oppose to 'bb', which confused me a lot. Does anyone understand why and give a explanation, please? Thanks! Promise.resolve('aa') .then(Promise.resolve('bb')) .then(console.log); 回答1: Well, you're misusing a .then() handler so it is no surprise that you don't get the desired answer. A .then() handler should be passed a function reference. You are passing it a promise which it dutifully

问题 I am having fun with Promises and have one problem. Here is my code req.checkBody(BookManager.SCHEME); req.getValidationResult() .then(function (result) { if (!result.isEmpty()) { handler.onError('Invalid payload'); return; } return new BookModel({ author: data.author, name: data.name, year: data.year }); }) .then((book) => { book.save(); }) .then((saved) => { handler.onSuccess(saved); }) .catch((error) => { handler.onError(error.message); }); But for some reason this then statement .then(

问题 I'm trying to use apolloFetch inside a Promise.all in my Node.js microservice but keep getting an error that the query is empty. The reason for using apolloFetch is to call another micro service and pass it an array of queries. Can someone give me some direction? My code is as follows: const uri = "dsc.xxx.yyyy.com/abc/def/graphql"; const apolloFetch = CreateApolloFetch({uri}); const QryAllBooks = { type: new GraphQLList(BookType), args: {}, resolve() { return new Promise((resolve, reject) =>