Importing Axios React

Here is an example App. ←Home Subscribe Getting started with React Native & Django authentication - Part 2 May 15, 2018 react-native django auth development. In the example below, I am using free coindesk API which gives Bitcoin price in different currencies. 이 강좌는 참고용으로만 읽어주세요. I've always found chris a great teacher. import axios from 'axios'; export function setToken (token) {axios. js file: import OpvSession from 'openvidu-react'; 2) Secondly, you need to install axios that allows you to do HTTP requests: npm install axios --save. /types' Then we can create the first action creator. ImageUpload. In Part 1 of this series we have created Nodejs API’s to perform CRUD operation. Async Redux: Connecting React to an External API. initialState, state and setState() helpers are good to show components in different states, but to let users copy-paste your example code without modifications into their React app you may want to use React. For the previous part check out: HTTP, Axios, Redux The source code is available at GitHub: React series - react-series-part4-end branch. js app up off the ground. Axios is promise-based and thus we can take advantage of async and await for more readable asynchronous code. The handleChange prop provides a function, which is triggered on user interaction with the component. Build Your First Java Full Stack Application with React and Spring Boot. js; How To Create React App. Using Axios library does not let my React application perform the POST method, however using Postman to perform the request it was able to consume the endpoint and save details on my local database. Default imports aren't named, so you can have anything. … I'll call this appointments. Let us say if various react components need to display the same data in different ways. It doesn’t matter what backend technology you are using (i. 8 and adds support for iOS 13's Dark Mode and Apple Authentication. Open up your code editor (I use Visual Studio Code), and navigate to /src/App. js; How To Create React App. Become a Full Stack Java Web Developer Now! Course Ratings are calculated from individual students’ ratings and a variety of other signals, like age of rating and reliability, to ensure that they reflect course quality fairly. It’s more readable and also It’s easier to use to display validation errors in the front end. /App' render(, document. The store catches the action and forwards it to the reducer. Sending an HTTP request to a server is a common task in web development. Redux helps in managing the state of your data, I'm not building a big application, but having an easy way to check what's in your state is definitely a plus. Sorry for the delay of this much awaited post. I use MongoDB as my database and I also use express-session library for storing the session and attaching data on it. GitHub Gist: instantly share code, notes, and snippets. import axios from 'axios' The Random User Generator API offers a bunch of options for creating various types of data. React is a JavaScript library that Facebook created to facilitate the development of Single-Page Applications (a. Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. React Native combines the best parts of native development with React, a best-in-class JavaScript library for building user interfaces. js: import { BrowserRouter} from ‘react-router-dom’;. Let us say if various react components need to display the same data in different ways. React is a JavaScript library that Facebook created to facilitate the development of Single-Page Applications (a. state = { total: 10, // 在this. Technology stack. React’s renderToString (and renderToStaticMarkup) methods are, unfortunately, synchronous. create({ baseURL: 'http. Note: you should import moment before using antd. js We install Vue. One of the most popular web application stack based on Node. js to see how you have imported it. Here are the steps to follow for using async/await in React: put the async keyword in front of your functions. import { observable, action, computed, useStrict } from 'mobx'; import axios from 'axios'; // First we’ll be importing the main building blocks of our application: MobX observables. I have an app where you can create many events, and I have created an API with express and node JS. Pen Settings. One particular user seemed a little frustrated with his/her understanding of React and had a few specific complaints about form data and submissions. 打开 cmd,运行msiexec /package 文件路径. Webpack will help us bundle all of our react and redux files into one large "bundle" file that will be used in our index. If you’re interested in Axios, check out my tutorial on Using Axios to Make API Requests in React. json … and I'm going to paste all that in there. So I completed this course and with bright future ahead of me I start to create my first own React based project. It involves simulating component interactions and mocking the API calls. First, let’s define a custom wrapper around Axios for our application. The Axios library can be used in your plain JavaScript application or can be used together with more advanced frameworks like React. Importing Axios. Let us say if various react components need to display the same data in different ways. It is ready to use and ships with Jest!. But where to put async/await in a React component? Used mostly for data fetching and other initialization stuff componentDidMount is a nice place for using async/await in React. It is not feasible to keep real DOM manipulations in sync with React's virtual DOM. Now let's see how we can consume JSON data from our third-party API endpoint using the Axios client. Good libraries positively affect architectural decisions and advocate best practices. This tutorial contains an introduction to Axios and shows you real-world use cases of the library CodingTheSmartWay. react와 spring boot 연동 깃은 따로 react만 사용했을 경우 input을 활용한 insert 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26. 个人搜集总结了vue 和 react的axios二次封装方法,便于大家对比使用:总体实现伪代码用例,用于配置axios,import axios from "axios"; import qs from "qs"; // react 中使用antd 此处自定义 // i…. js, Meteor, React and Angular!. Take a look at it, and we'll go over how it works. Here, we want to display user message suppose, so we make a component and initialize with initial state. import axios from 'axios' The Random User Generator API offers a bunch of options for creating various types of data. In the first section, we will be using the browser's in-built Fetch API to request external data asynchronously. 0 SDK which now supports the Firebase Realtime Database and Firebase Authentication. First, we need to install the axios http client library from the npm. Hi! I have finally managed to get adal. The render() lifecycle method is mandatory to output a React element, because after all you may want to display the fetched data at some point. Is this axios, npm package or some file in your project? How are you importing it? Please share the code of src/Component/Form. 0 on GitHub (npm) Changelog Welcome to the 0. React simply renders components, using data from only two places: props and state. … I'll call this appointments. net backend hosted in azure. 3 of the Most Common Errors in React Since I began programming I have been writing errors in my code. 0 release, breaking changes will be released with a new minor version. // import dependencies import React from 'react' // import react-testing methods import from 'react' import axios from 'axios' export default function Fetch. While making a Single Page App with React, it is very easy for your code-base to become unorganized. Quick Start. In the previous chapters, we have learnt what is Redux and how it works. Pieces of state that cause reactions and computations in response to their own changes. I love the 'services' architecture of making requests in Angular, and wrote this little wrapper (and instructions) for my React and other JS projects. Setup Setup with Create React App. The ability to login and make authenticated network requests to a backend API are often required, but not always easy to implement. シンプルなCRUD(create, read, update, delete)アプリをデータベースはmysql, フロントエンドはReact + Reduxで作ってみます. Run the following command in the root folder of your react projects. You will learn how to do both, so let’s go! Mocking. This new function will essentially be a container. But with the addition of API Routes, Next. createConnection - can I specify clients port. Pen Settings. React doesn't prescribe a specific approach to data fetching, but people commonly use either a library like axios or the fetch() API provided by the browser. React dates, React infinite calendar, Dayz, Input moment, React big calendar, React yearly calendar, React toolbox, Grommet, React datetime, React daterange picker, React bootstrap daterangepicker, React datepicker, React day picker, React input calendar, React calendar, Ga date picker…. js componentDidMount()` lifecycle phase I have an axios get request to a rest service. Questions: I have a react/redux application that fetches a token from an api server. I was reading through a thread on Reddit recently with some users discussing React. In this post: we will show you how to use Redux in React Application and how to use Axios to send the HTTP requests from React app. Axios is a promise-based HTTP client that works both in the browser and in a node. A common thing is for our application to fetch some data from. ←Home Subscribe Getting started with React Native & Django authentication - Part 2 May 15, 2018 react-native django auth development. A simple import will do, and you don’t need to import it everywhere; that’s why we have service caller wrappers. Hi! I have finally managed to get adal. For the first part please check here. Especially the one that renders the form. bind the "contacts" prop of ComponentList to App component's State to pass the contact data. In this tutorial, we’ll tie those together and then use Stormpath to add authentication and authorization protocols. The render() lifecycle method is mandatory to output a React element, because after all you may want to display the fetched data at some point. For instance, when a to-do list renders, each item must "remember" whether it was checked off. axios: Promise based HTTP client for the browser and node. Axios 如何发送, 端口不一致, 使用 proxy 配置转发 axios 拦截器, 同意 loading 处理 redux 里使用异步数据, 渲染页面 示例 安装npm. I would not explain why Axios is more popular than FETCH or other APIs in both React. One of my favorite things was the services architecture of making requests. state = { userList: [] }; } componentWillMount() { axi. This guide helps you create a full stack application secured with Basic and JWT Authentication using React as Frontend framework, Spring Boot as the backend REST API and Spring Security as the security framework. js We install Vue. The following is the action which makes the network request that I want to test. In this tutorial, we will learn how to upload images or files from a React Js app with Spring MVC Rest. Are you working on JWT authentication in React and Redux App? You don't know how to handle it? In this article we will cover a sign-in process step by step. Despite initial skepticism, React Native is very much in demand today! In this article, Toptal Freelance React Native Developer, and former React Native skeptic, Alexander Pataridze talks about why he became a React Native advocate instead and introduces us to the technology by illustrating four use-cases. I've always found chris a great teacher. A best practice of React. In this article, I'll explain about how to upload a file using axios and redux-form First, you need to download required packages using npm. It's an anti-pattern to interact with the store directly in a React component, whether it's an explicit import of the store or accessing it via context (see the Redux FAQ entry on store setup for more details). MERN Stack is a combination of four technologies — MongoDB(M), Express(E), React(R), NodeJS(N). 1、前言 之前我们已经介绍了如何:新建一个react项目,并介绍了基本的路由配置、less、以及ui的使用。 接下来将会介绍在React如何使用axios实现前后端交互。. Axios nos permite definir una instancia base en la que podemos definir una URL y cualquier otro elemento de configuración. Axios Promises Reusable UI State Push CSS Transitions ES6 let / const import /export import React, { PropTypes }. Also imported is a ResultsTable component. state = { total: 10, // 在this. The redux-devtools one is useful for logging and analyzing the evolution of the store in a Chrome extension for example. Both React and MobX provide an optimal and unique solutions to common problems in application development. 0) released. If you are new to React, we recommend using Create React App. Component · render() · componentDidMount() · props/state · dangerouslySetInnerHTML · React is a JavaScript library for building user interfaces. In this MobX + React tutorial we'll build a List Detail View Component as our first app. First, let’s define a custom wrapper around Axios for our application. Aborting An XHR Request In Axios “Do, or do not. From the very beginning, we need to stress that Redux has no relation to React. 0 release, breaking changes will be released with a new minor version. A common thing is for our application to fetch some data from. Now delete everything from the directory react-rest/src but do not delete src directory. Until axios reaches a 1. I am also going to use the Axios promise based library to give you an idea on how to fetch data online. Skip to content. … Go ahead and save that, and then in here … I'll go ahead and import axios from the axios library. JsonWebToken (JWT): it is a compact and self-contained way for securely transmitting information between parties as a JSON object. To fetch data in React, there are many HTTP libraries available like - Apollo, Axios, Relay Modern, Request, and Superagent. First things first, create your CometChat app. The only thing worth mentioning in the dev dependencies is webpack and volleyball. Adding the Enzyme test utilities to the mix makes testing simple React components a breeze. Then import this component to client/src/Form. js; Supports the Promise API; Intercept request and response. So let’s install that now: _npm i -S axios_. Then import this component to client/src/Form. Today we will create an Avengers series app by using the same stack and the powerful Ionic Component API. but in this blog, we will give the example based on redux promise middleware with axios. Redux helps in managing the state of your data, I’m not building a big application, but having an easy way to check what’s in your state is definitely a plus. js which is where we'll work for the remainder of this tutorial. Let's add the Axios module to our application by importing it into our App. When axios library is integrated, you can easily use it to make Ajax requests from your react application. In addition, we’ll dig into the inner workings of Redux so that you better understand when and how to apply Redux to your current (or next) React application. js with the help of examples. getXxxData()里面通过axios获取,传递给表格子组件。. Until axios reaches a 1. Check out code samples to build a contact form with React. At the moment we are only utilizing the axios. How do I export axios get request from separate. In the example below, I am using free coindesk API which gives Bitcoin price in different currencies. The store catches the action and forwards it to the reducer. use(getAuthToken(this. Axios: it is a Promise-based HTTP client which we will use to communicate with the Node server. import Axios from "axios"; Many use Axios or axios, but it really doesn't matter because it's a default import. [React / React Naive TIPS] axios 와 fetch 어떤 것을 사용할까? * 해당 글은 구글 검색 'what difference fetch axios' 라고 검색했을 때 나오는 1 페이지의 내용을 기반으로 제 생각이 첨가되어 작성되었습니다. > npm install axios --save. 如果遇到 windows 没有权限安装 msi 文件. React applications generated by create-react-app provide a pre-configured Jest test runner. In this post, we'll break down the 'URL Parameters' example on the React Router documentation to learn how you to effectively leverage URL parameters in your React app. firs time use external app to access gmail, google will email security alert turn less secure app on home controll. Are you a newbie to React, and using this generic style to upload files on the web?. Axios 如何发送, 端口不一致, 使用 proxy 配置转发 axios 拦截器, 同意 loading 处理 redux 里使用异步数据, 渲染页面 示例 安装npm. Relay Modern - A JavaScript framework for building data-driven React applications. You should request your api in a separate file and call your action when the result comes back. Create RestController. Intro This is Part I of a eight part series on building a CRUD application with React + Redux. Upload Multiple Files To Cloudinary Using React Dropzone & Axios We had a requirement in one of our recent client's project to provide a lot of file uploading. I have an app where you can create many events, and I have created an API with express and node JS. React-router-dom; CMD: npm i [email protected] Axios is a lightweight HTTP client based on the HTTP service and similar to the Fetch API. It is ready to use and ships with Jest!. axios is the promise so you need to use then to get your result. Axios (stylized as AXIOS) is an American news and information website founded in 2016 by former Politico staffers Jim VandeHei, Mike Allen, and Roy Schwartz. You can check the documentation for further information, but for this tutorial, we will keep it simple. A web developer gives a tutorial on creating an application that accetps file inputs using React. The render() lifecycle method is mandatory to output a React element, because after all you may want to display the fetched data at some point. React is a JavaScript library that Facebook created to facilitate the development of Single-Page Applications (a. React dates, React infinite calendar, Dayz, Input moment, React big calendar, React yearly calendar, React toolbox, Grommet, React datetime, React daterange picker, React bootstrap daterangepicker, React datepicker, React day picker, React input calendar, React calendar, Ga date picker…. That's why the render() method is mandatory in React class components: The React Component from the imported React package instructs you to use it for displaying something in the browser. // import dependencies import React from 'react' // import react-testing methods import from 'react' import axios from 'axios' export default function Fetch. 这段代码使用 axios POST 登录信息到我们的 /auth endpoint,然后将返回的 token. Now let's see how we can consume JSON data from our third-party API endpoint using the Axios client. Are you a newbie to React, and using this generic style to upload files on the web?. 0 on GitHub (npm) Changelog Welcome to the 0. 15 you can Read more…. Using Axios library does not let my React application perform the POST method, however using Postman to perform the request it was able to consume the endpoint and save details on my local database. I have an app where you can create many events, and I have created an API with express and node JS. In the example below, I am using free coindesk API which gives Bitcoin price in different currencies. You get to render all the basic HTML components, and make them look good with CSS libraries like Bootstrap. We will create simple React. You can write Redux apps with React, Angular, Ember, jQuery, or. This new function will essentially be a container. js file under src directory with below content. You can add any view layer to Redux. Later calls use React's DOM diffing algorithm for efficient updates. axios is a peer dependency and needs to be installed explicitly. In this tutorial, we'll be looking at how to accept payments within a React Native app. Unless a size is specified, images will use the original dimensions of the image up to the size of its container. React renders the application state by providing mechanisms to translate it into a tree of renderable components. js offers a way to do that in just minutes. Sorry for the delay of this much awaited post. Fortunately, with the addition of API Routes, Next. js src/module/edit. With the help of axios - a promised based http client - we can concentrate on creating the request action and the reducers that deal with the respective outcome. Fiddling around with axios and react Fiddling around with axios and react 1 2 3. This article is the concluding part of the series on React App With Laravel RESTful API Endpoint. Axios is promise-based and thus we can take advantage of async and await for more readable asynchronous code. Axios (stylized as AXIOS) is an American news and information website founded in 2016 by former Politico staffers Jim VandeHei, Mike Allen, and Roy Schwartz. One of the key features in Single Page Applications is a little thing known as authentication. Especially the one that renders the form. js, and Twilio Programmable Video we create a Video Chat application. For the complete navigation and all the basic instructions of the React series, check out: Introduction to the React series. First: React itself doesn’t have any allegiance to any particular way of fetching data. The first import is needed in every component file. It's an anti-pattern to interact with the store directly in a React component, whether it's an explicit import of the store or accessing it via context (see the Redux FAQ entry on store setup for more details). Using React, Node. interceptors. As React is just a library for the user interface, it only knows about Props and State so here, HTTP comes into the picture. React only writes patch updates to the DOM, but never reads from it. React can be used as a base in the development of single-page or mobile applications, as it is optimal for fetching rapidly changing data that needs to be recorded. js to see how you have imported it. react-axiosAxios Component for React with child function callback. If you are using Redux or just a plain React app, you can add your AJAX calls inside containers. It can take a long time to get a full-stack React & Node. Do you want to learn how to build a Laravel React CRUD (create, read, update, delete) application using Laravel and React JS?If so, I am here to help you out. This tutorial help to consume CRUD API using Axios React. Because we want to avoid real HTTP requests during testing we'll have to mock the Axios library for this test, and because of the async nature of this code we'll have to utilize the waitForElement function again to wait until expected element has been rendered by our component. Let's add the Axios module to our application by importing it into our App. This is a well known package that is used in tons and tons of projects. Today we will create an Avengers series app by using the same stack and the powerful Ionic Component API. To complete MVC architecture we use Redux, flux, we will discuss those in other articles. You should request your api in a separate file and call your action when the result comes back. Check out code samples to build a contact form with React. js src/module/edit. In this tutorial, we will learn how to upload images or files from a React Js app with Spring MVC Rest. Relay Modern - A JavaScript framework for building data-driven React applications. Now will install dependencies – npm install. use(getAuthToken(this. Now in this blog post I am going to show you how you can make use of that JWT auth server in an react application. First, we need to install the axios http client library from the npm. Please read this guide first if you have any question on our application structure, file names, TypeScript conventions…. Install Axios can be… This app works best with JavaScript enabled. Axios is a promise based HTTP client for the browser and Node. js file: import OpvSession from 'openvidu-react'; 2) Secondly, you need to install axios that allows you to do HTTP requests: npm install axios --save. First things first, create your CometChat app. Some Redux is used as well for storing global app state. If you're interested in Axios, check out my tutorial on Using Axios to Make API Requests in React. 8) as they bring along great. The value prop manages the component’s state, making it a React controlled component. e Nodejs, WordPress etc) you can fetch data from the…. Ajax then you have to load the complete JQuery library instead Axios is specially made to support Ajax calls, much smaller. When that response comes back with the payload of all the cats, it will dispatch a new action that contains the cats payload. Do you want to learn how to build a Laravel React CRUD (create, read, update, delete) application using Laravel and React JS?If so, I am here to help you out. Fetching Data with Axios 4:32 with Guil Hernandez Learn to make server requests in React using Axios, a promised-based library that's similar to the Fetch API. Fetch will send request to the server for any given resource which returns promise. In this blog post, we’ll outline why we’ve decided to use the oh-so-popular React state container, Redux, to help us keep our code for Cabin clean and tidy. What will we be building? With cryptocurrency taking the world by storm, creating a cryptocurrency ticker app is the perfect way to use many different React features to build a functioning finished product that is actually usable. Take a look at it, and we'll go over how it works. import axios from ". Axios (stylized as AXIOS) is an American news and information website founded in 2016 by former Politico staffers Jim VandeHei, Mike Allen, and Roy Schwartz. In this tutorial, we are going to learn about post request in the react. Quick Start. React Native Coach Bringing you the best React Native, GraphQL, Redux, and Mobile Design resources from around the web. Building Live Streaming App with Node. If you already have react installed in your project and you just want to add existing dropdown functionality, feel free to skip this part. You finally have a fledged-out React component, but how can we get actual data from our APIs?. react使用ajax可以選用fetch API或react-axios,react-axios是把axios在包裝成components,所以可直接使用標籤方式呼叫ajax,但安裝使需注意dependancies。 fetch API或直接使用axios,呼叫時注意react生命周期。. In this tutorial, I have coded the MERN Stack Tutorial. In this tutorial I will show you how to fetch data from an api to your react app. URL parameters are a fundamental aspect of React Router and a fundamental aspect of building web applications. js already set up out of the box. We can rewrite the example above like this: // ```jsx inside Markdown class ModalExample extends React. Specify this option depending on the behavior you implemented for the load function. So type the below command on a terminal. React dates, React infinite calendar, Dayz, Input moment, React big calendar, React yearly calendar, React toolbox, Grommet, React datetime, React daterange picker, React bootstrap daterangepicker, React datepicker, React day picker, React input calendar, React calendar, Ga date picker…. The two are connected by API calls using axios in the frontend. Most of the React and Ember projects I work on use Axios to make API calls. To power your chat application, you'll be using CometChat. com is a blog about latest technologies in web development, including Node. js is replacing Angular and React in many cases. 이 강좌는 참고용으로만 읽어주세요. Inside of my main `App. To get started, we'll install the react and react-dom npm packages, then create files for two components: PlanetSearch and Planet. A web developer gives a tutorial on creating an application that accetps file inputs using React. A common thing is for our application to fetch some data from. … I'll call this appointments. Beginner Tutorial Objectives of this tutorial. Now in this blog post I am going to show you how you can make use of that JWT auth server in an react application. For the complete navigation and all the basic instructions of the React series, check out: Introduction to the React series. To learn more about fetching data from an API in a real application, check out our tutorial on building a complete React app with Airtable. React Grid examples and demo on this page. Async Redux: Connecting React to an External API. We will have a React app with and without Axios integrated with it to push selected files in the browser to the server via REST. manual ( false) - If true, the request is not executed immediately. Being a developer we are quite used to the whole uploading process & the time it takes on the internet. Container configuration. Therefore, we can use Axios with React to make requests to an API, return data from the API, and then do things with that data in our React app. This guide helps you create a full stack application with all the CRUD (Create, Read, Update and Delete) features using React as Frontend framework and Spring Boot as the backend REST API. If you want to look at part 1 here is the link. Also imported is a ResultsTable component. common ['Authorization'] = `Bearer $ `;} Option 4: Pass the Value From a React Component It's simple to get access to the store inside a React component - no need to pass the store as a prop or import it, just use the connect function from React. React中配置Sass引入. To fetch data in React, there are many HTTP libraries available like - Apollo, Axios, Relay Modern, Request, and Superagent. I'm trying to consume an API in my react application using axios. As the name suggests, I have used MongoDB as a database, Express as a node js web framework, React js as a front-end framework and Node js as a backend platform. You get to render all the basic HTML components, and make them look good with CSS libraries like Bootstrap. In fact, you could watch nonstop for days upon days, and still not see everything!. This tutorial contains an introduction to Axios and shows you real-world use cases of the library CodingTheSmartWay. TL;DR: In this post, you will learn how to develop web applications using React and Symfony. The Axios library can be used in your plain JavaScript application or can be used together with more advanced frameworks like React. keys The list-items have memory from one render to the next. js src/module/edit. Then, simply require/import React, enzyme functions, and your module at the top of a test file. This is our preferred method as it allows the. I will discuss how you can use it with axios, but I first wanted to show the in-depth under-the-hood version of how AbortController works. render() controls the contents of the container node you pass in. In the second part of our series on the MERN stack, we complete our project by connecting our back end to our React-based front end. Doing so pulls in only the specific components that you use, which can significantly reduce the amount of code you end up sending to the client. You should request your api in a separate file and call your action when the result comes back. Redux helps in managing the state of your data, I'm not building a big application, but having an easy way to check what's in your state is definitely a plus. HTML preprocessors can make writing HTML more powerful or convenient. In this blog post, I will present quick code snippets on how to test your React component. Inside of my main `App. Later calls use React's DOM diffing algorithm for efficient updates. For the sake of this demo this can by any component we’ve created to display our data such as a table, list, menu tree, whatever. To complete MVC architecture we use Redux, flux, we will discuss those in other articles. import React from 'react'; import ReactDOM from 'react-dom'; import axios from 'axios'; class FetchDemo extends React. react와 spring boot 연동 깃은 따로 react만 사용했을 경우 input을 활용한 insert 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26. Now delete everything from the directory react-rest/src but do not delete src directory. Axios Axios is an open source Javascript library that allows us to make HTTP requests, that works in both Browser and Node. For our getting started tutorial, we are going to use the trivial Counter demo from the Redux repo.