es6-promise

Can anyone explain how does jest.fn() actually work with a real world example , as i'm literally confused on how to use it and where it has to be used. For example if i have the component Countries which fetches country List on click of a button with help of the Utils Function export default class Countries extends React.Component { constructor(props) { super(props) this.state = { countryList:'' } } getList() { //e.preventDefault(); //do an api call here let list = getCountryList(); list.then((response)=>{ this.setState({ countryList:response }) }); } render() { var cListing = "Click button to

I have a promise and I want it to resolve only when inner promise has resolved. Right now it resolves before the "resolve" function has been reached in the "loadend" callback. What am I missing? I am confused about the way you are supposed to use resolve and about how you can use a promise within another promise. I couldn't find anything that helped on the web. In the following example I basically load a bunch of files, for each file I get a blob and I want to pass this blob in a file reader. Once all files have been passed to the file reader, I want to move to the next function in the promise

How to make server-side validation using redux-form and Fetch API? There are " Submit Validation " demo provided in the docs which says that recommended way to do server side validation is to return a promise from the onSubmit function. But where should I place that promise? As I understood onSubmit function should be my action. <form onSubmit={this.props.addWidget}>... Where this.props.addWidget is actually my action, provided below. import fetch from 'isomorphic-fetch'; ... function fetchAddWidget(widget, workspace) { return dispatch => { dispatch(requestAddWidget(widget, workspace)); return

Does anyone know, using Modernizr or otherwise, if there is a way to detect if the Promise feature is enabled in a browser? I have a polyfill for the functionality, but only want to apply it if the browser does not have a native implementation. Update Dec 11 - 2016: All evergreen versions of browsers now support promises. They are safe to use. Update Nov 14 - 2016: Chrome, Firefox, Safari and IE all now have experimental support for promises in their dev channels. The specification has settled. I would still not rely on the implementation just yet and would use a library but this might change

So i've read that observables are looking to overtake promises in terms of usage in some of upcoming JavaScript MVC's: Angular 2.0 Falcor used by Netflix What is the difference between observables and promises? Updated: Apologies! removed my falsy statement. What is the difference between observables and promises? Simply put: A promise resolves to a single value asynchronously, an observable resolves to (or emits) multiple values asynchronously (over time). Concrete examples: Promise: Response from an Ajax call Observable: Click events More information can be found here: http://reactivex.io

I am putting catches at the end, but they are returning empty object in one particular instance at least. Is a catch necessary for anything unbeknownst, or is it just screwing me up? $( document).ready(function(){ app.callAPI()//a chainable a RSVP wrapper around a jquery call, with its own success() fail() passing forward to the wrapper, so it will either be a resolved or rejected thenable to which is now going to be chained .then( function(env) { //set the property you needed now app.someSpecialEnvObj = env; }, function(rejectMessage){ console.log('call.API() cant set some special env object.

My idea is. I have limited number of workers. This workers must do some job. When worker done with job, then he must take other job, until complete all the jobs. I write this code: function createWorker(num){ this.num = num; this.Run = (job) => ( new Promise( (resolve, reject) => { setTimeout(() => { resolve({worker: this, num: this.num, job: job}); }, 5000); } ) ); } function Processing(maxWorkers, jobs){ this.Workers = []; this.Jobs = jobs; this.Go = () => { return new Promise( (resolve, reject) => { while(true){ let worker = this.Workers.pop(); if (!worker) continue; let job = this.Jobs.pop