Getting Started with React

Slides: j.mp/getting-started-react GitHub repo: github.com/t7/react-starter Me, on Twitter: @nathansmith

• Father of two rambunctious boys, who are big fans of Star Wars and Legos.  • Self-taught. That just means I pestered lots of people until I learned how to do this stuff. Yet, I still doubt myself daily.  • I build the "legacy" software of tomorrow.  • I generally have a "get off my lawn" attitude towards emerging technology. Nathan Smith Principal Front-End Architect Introduction

Scientific* comparison of "React.js" versus "Angular.js" *Not really scientific.

Perhaps unsurprisingly, my off the cuff, ill-informed reaction… ended up being totally wrong. (But, admitting when you're wrong is part of being a grown-up, right?)

©2015 T7 Software development is a field in which it is actually possible to know less % overall, even if you were to never forget anything. There are always new things to learn, because the total surface area is continuously expanding.

Today, I would like to talk to you about the "three Rs." •Reading •wRiting •aRithmetic

There are three fundamental aspects of most React apps. •React = the "V" (and "C") layer. •Redux = the "M" layer. •Router = um, the "URL" layer? :)

PROOF POSITIVE OF COOL PROJECTS? LOGOS! github.com/reactjs/react-routergithub.com/reactjs/reduxgithub.com/facebook/react

Actually, my projects are more like this. Accounting.js Babel ECMAScript 6+ ESLint Jest Lodash Markdown Moment.js NPM PostCSS React ReactDOM React Router React Test Utils Redux Sass (SCSS) Sass-Lint Standard Webpack window.fetch

npm init -f && npm install --save-dev accounting autoprefixer babel-core babel-jest babel-loader babel-plugin-transform- runtime babel-preset-es2015 babel-preset-react babel-runtime copy-webpack-plugin cross-env css-loader es6-promise eslint eslint-config-standard eslint-config-standard-jsx eslint- config-standard-react eslint-plugin-promise eslint-plugin-react eslint-plugin-standard exports-loader extract-text-webpack- plugin html-webpack-plugin husky imports-loader jest-cli json- loader lodash marked moment node-sass postcss postcss-loader raw-loader react react-addons-test-utils react-dom react-hot- loader react-redux react-router redux rimraf sass-lint sass- loader style-loader webpack webpack-dev-server whatwg-fetch

How I feel when there's a learning curve. (Don't worry, you're not alone.)

NOTE: First off, let me say that what I am showing you today is simply "a" way to do React. It is not necessarily "the" (right, only) way. This is simply the approach we have settled on, after trial and error with various projects.

One thing to keep in mind when working with React is the oft-repeated phrase… "Everything is a component." A component is essentially anything that looks like this: <UppercaseTag> (Components may contain other components.)

Any time you see something like this… <UppercaseTag /> <UppercaseTag> content </UppercaseTag> …that is usually a React "class," which may or may not be an actual JavaScript (ECMAScript 6) class. For the purpose of this talk, let's assume they all are.

NOTE: Syntax that looks like HTML but is embedded (not simply within a string) in JavaScript is referred to as "JSX." It is an artificial construct that means: React.createElement(UppercaseTag, …)

Conceptually, all React apps are structured like this. – great-grandparent –– grandparent ––– parent –––– child –––– child –– grandparent ––– parent –––– child –––– child

Components talk to each other via "props." <UppercaseTag foo='bar' /> ^ Here, the parent of <UppercaseTag> is passing down a prop called foo, with the value of 'bar'. Within the UppercaseTag class, that is usable via… this.props.foo // "bar"

Typically, in order for a child to talk to a parent, the parent component passes a callback function prop to the child. Here's an example of how we use our <Input /> component. <Input handleChange={ function (e, value) { // `e` is the event. // `value` is the *.value of the input. } } />

Q: What if the parent does not "care" about the grandparent or the child, other than the fact that they are nested within one another? – grandparent <—> "parent" props –– parent <—> "grandparent" and "child" props ––– child <—> "parent" props

A: That is why Redux was created, to allow each component to get and/or set changes to a shared object store, aka "app state." – grandparent <—> Redux –– parent ––– child <—> Redux ^ If the parent has no inherent reason to care about the shared state, it need not be involved as an unnecessary middleman.

NOTE: Dan Abramov is on the React team, and is the creator of Redux.

NOTE: Ryan Florence is one of the creators of React Router. He does not usually use Redux.

You may sometimes hear about local state as being confined to each individual React component. That is correct. Components can have... this.state.batmanIdentity // "Bruce Wayne" this.state.checked // boolean this.state.hasPlaceholder // boolean this.state.value // string …data that is internal. That self-contained state can be shared with child components via props, and can be passed to parents via callback functions. Redux "app state" makes things like this.props.foo available to multiple components, from a source other than their parents. Redux is a "parent to all."

©2015 T7 I think of the relationship between HTML & JS like this: Using jQuery or Angular is like decorating trees in a forest. Using React is like planting a magic seed, from which a decorated forest grows.

Angular apps usually have "decorated" HTML, with <tag ng-foo="…"> attributes sprinkled throughout. HTML loads, JS parses it, and then applies functionality.

React apps usually have a very minimal HTML page, with a single insertion point, such as <div id="app"> and then the rest of the markup is generated entirely by JS.

Having full knowledge of the generated HTML, React is able to keep track of the "virtual DOM" and do precise updates accordingly. This means you rarely, if ever, actually make any of your HTML changes directly. No more typing… $('#foo').addClass('bar')

Anatomy of a React Component NOTE: This is an contrived example. You would not normally use internal state, when something is just directly set via props anyway. However, this illustrates the relationship between state and props. State is internal, whereas props come from a component that resides a "level above."

Anatomy of a React Component NOTE: Most of the time, you can safely leave out the constructor. It is called implicitly, if absent. This example also shows how you might use defaultProps, to provide a fallback placeholder for this.props.name. This is handy when awaiting an Ajax request.

My React apps normally follow this hierarchy: – <Provider>..........................// Redux. –– <Router>...........................// Router. ––– <RouterContext>...................// Router. –––– <Connect>........................// Redux. ––––– <Page>..........................// mine. –––––– <App>..........................// mine. ––––––– <AppMain>.....................// mine. –––––––– <ParentComponent>............// mine. ––––––––– <ChildComponent>............// mine! –––––––––– // etc.

©2015 T7 Let's walk through the structure of the T7 React starter project. First, we will look at the initial index.js file, and then progress further into the "nested" JS components from there. Lastly, we will fire it up in the browser.

How I feel about neatly nested nested React components. bestpysanky.com/9-pcs-10-Semenov-Russian-Nesting-Dolls-p/nds09000.htm

This index.js file kicks off the entire app. It pulls in <Provider> as the first component, which wraps {routes} and makes shared Redux "app state" available.

In routes.js we have the pattern matching of various paths, and their respective components. We are also setting a title prop that will be added to the <title> tag via a Page component.

This a simple <Page> level component. In this case, it is the fallback for when a route is not found. We are pulling in a Markdown file, with a basic "404" message. It utilizes the <App> layout component, wrapping the content.

This is an example of the <App> layout component, which pulls in app level header, main, footer, etc. {this.props.children} is the Markdown content, passed forward from the <Page> component.

This is the <AppHeader> component, which was being used from within the <App> component. It contains the logo, and a few links in a list. It is making use of the "Unsemantic" grid, via <Grid> components.

Here, the <AppMain> component is basically just a pass-through for content, simply wrapping it in <main role="main"> for accessibility and styling purposes.

©2015 T7 So, that covers some of the app structure... – index.js – routes.js – various "page" and "layout" components Next, let's take a look at <Accordion>. It is a component that maintains internal state, but can also be overridden by its parent.

Accessibility is best when done with advanced planning. For the components we build, we make sure it is not just an afterthought.

This is actually an example of the <AccordionMulti> component, a not mutually exclusive version of the <Accordion> component.

First, the initial selected state is set, based on props passed in from the parent component. If it does not exist, then the accordion starts out completely collapsed. We also ensure a unique id, to map ARIA roles to various elements.

In the event that the parent component wants to override the internal state, we have componentWillReceiveProps which will potentially cause a state change by calling… this.setState({key:val})

The handleClick method is called internally when an accordion header is clicked. This sets the component state, and if a this.props.handleClick callback exists from the parent, it will call it too.

Here, an otherwise tedious process is made fully automatic. That is, obviating the manual assignment of a unique id to each header and panel, in order to ensure ARIA accessibility hooks are properly associated to their peer elements.

In the render method, ARIA roles are set, based on the internal component state. For each section of accordion content, a child component <AccordionHeader> is created. Also note, an accordion is technically a role="tablist"

©2015 T7 Okay, so now we have a basic understanding of how an accessible component works. Let's now delve into how we can persist component state across <Router> changes, and potentially even across page reloads. We will take a look at how a <Page> level component is hooked up to Redux.

<Page> is like Tony Stark. Redux connect adds the "suit" to this.props This is done through a process called "currying," when a function returns another, modified function.

First, we need to import bindActionCreators and connect from redux, and react-redux. These will allow us to make external functions usable within the <Page> component.

Next, we import our own "actions" from the various files we have stored in the directory "/source/redux/actions". This directory is not to be confused with NPM's "/node_modules/redux".

At the end of the file, we have Page.propTypes validation, so that React can warn us if the wrong type of props are passed. string vs. boolean, etc.

mapStateToProps is where external "app state" is added to <Page> via this.props.*

mapDispatchToProps is where external functions are made available to <Page> via this.props.*

Lastly, connect uses "currying" to make these changes innate to <Page>. You could think of <Page> as Tony Stark, and the result of the connect call as wrapping him in an Iron Man suit. <Page> then has all the additional props and functions applied to it from Redux.

Thanks to the aforementioned currying of connect, we now have multiple "action" methods available from Redux, that can be called from within our <Page> component.

When we actually make use of <AccordionMulti> we pass in the selectedFaqAccordion "app state," and the callback handleClickFaqAccordion which triggers our Redux "action" state change.

©2015 T7 Alright, so that is how things work on a component level. But what is all this talk of mapping state, mapping dispatch… Where does that come from? Glad you asked. Next, let's look at these Redux concepts: actions, action types, and reducers.

The way Redux layers together various state changes into one object reminds me of the SNL skit "Taco Town" where they wrap a hard-shell taco in a soft-shell taco, in a crepe, in a pizza, in a pancake, that is deep fried…

In "/source/redux/index.js" we have what is referred to as a rootReducer, which aggregates the various child reducers. A common mistake is to forget to add a new reducer here. That can lead to frustration when debugging.

In "/source/redux/_types.js" there is a list of action types, which have been assigned to constants. While this may seem silly, because they are just strings, it enforces unique action names. This is helpful as your project grows larger.

Each reducer reads from the aforementioned _types.js file, and potentially pivots based on what type of action it is. In this case, we are saving changes to the selected state of the accordion. Notice that the state is being get/set by utils.storage, which allows the state change to persist across page loads, saved in window.localStorage

This file makes the function this.props.updateFaqAccordion available to any component where connect is used on it. It passes forward any changes to the accordion's selected state.

By default, Jest wants to be helpful and "mock" every file you include. But, we can just disable that, as we know exactly what we want to test. It speeds things up.

We give our test suite a name, the same as our <UppercaseTag>. Then, we render it into the testing concept of a "document," and assign a parent reference. Then we can use vanilla DOM methods: querySelectorAll, etc.

For each aspect we want to test, we pass a string and function to "it" — made available by Jest. it('does something', …) Each resulting pass/fail is shown in the command line, via… npm run test

©2015 T7 Across various projects, we find it helpful to have a set of utility methods, which we use by attaching them to a parent object, utils. Allow me to explain a few of the cool and/or more frequently used methods: — utils.ajax — utils.save

In the "/source/utils/index.js" file, we import various utility methods, and bundle them under a single object, named utils.

In the "/source/utils/_ajax.js" file, we have a wrapper around window.fetch — which is the new HTML5 replacement for the quirkiness of XMLHttpRequest. You can specify a host, url, method, params — sent as query or body based on method — and callbacks for success/error. This file is not presently used in the React starter project, but we do make use of it in real projects that require us to do Ajax.

I use this utils.save method quite a bit, when I need to view an API response that is too cumbersome to read as JSON in the browser's developer tools. Instead, it causes the browser to download a nicely formatted *.json file, so I can scroll through it using a text editor instead.

Clicking the Save JSON button on the "/#/profile" page of the demo app will download a JSON file… form_data.json In it, you will see the current state of the form fields and their values.

Resources: • facebook.github.io/react/docs/tutorial.html  • reactforbeginners.com  • egghead.io/series/react-fundamentals  • egghead.io/series/getting-started-with-react-router  • egghead.io/series/getting-started-with-redux  • code-cartoons.com/a-cartoon-intro-to-redux-3afb775501a6  • medium.com/@learnreact/container-components-c0e67432e005  • medium.com/@dan_abramov/smart-and-dumb-components-7ca2f9a7c7d0

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