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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Learning React - Basic rendering</title>
<meta name="apple-mobile-web-app-capable" content="yes" />
<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no, minimal-ui">
<link rel="icon" type="image/x-icon" href="mc2/images/favicon.ico">
<link rel="stylesheet" href="mc2/styles/reveal.css">
<link rel="stylesheet" href="mc2/styles/theme.css" id="theme">
<link rel="stylesheet" href="mc2/styles/code.css">
<link rel="stylesheet" href="styles/react.css">
</head>
<body>
<div id="pos"></div>
<div class="reveal">
<div class="slides">
<section class="slide chaptertitle">
<div class="slidecontent">
<div class="chapternumber"> chapter 4 of 14 </div>
<h1>Basic rendering</h1>
</div>
</section>
<section class="slide sectionlist">
<div class="slidecontent">
<h3>Sections in this chapter</h3>
<ol>
<li><a href="#/2">Enter React</a></li>
<li><a href="#/3">Nested components</a></li>
<li><a href="#/4">Walk‑through 1</a></li>
<li><a href="#/5">Exercise 1</a></li>
<li><a href="#/6">JSX Basics</a></li>
<li><a href="#/7">Translation issues</a></li>
<li><a href="#/8">Walk‑through 1B</a></li>
</ol>
</div>
</section>
<section>
<section class="slide sectiontitle">
<div class="slidecontent">
<div class='sectioncount'>Section 1/7</div>
<h3>Enter React</h3>
<p>There's a new sheriff in town</p>
</div>
</section>
<section class="slide" data-pos="4-1-1">
<span class="pos">4-1-1</span>
<div class="slidecontent"><p>Here's the <strong>first thing</strong> you should <strong>learn about React</strong>: it is, at its heart, a <strong>templating solution</strong> for dynamic web sites.</p>
<p>That means that React <strong>converts data to UI</strong>. Commonly this step in an application is called the <strong>View layer</strong>, also known as the <strong>V in MVC</strong>.</p>
</div></section>
<section class="slide" data-pos="4-1-2">
<span class="pos">4-1-2</span>
<div class="slidecontent"><p>(...although React is <strong>more than that</strong>, but this is where we start!)</p>
</div></section>
<section class="slide" data-pos="4-1-3">
<span class="pos">4-1-3</span>
<div class="slidecontent"><p>At <a href="https://www.youtube.com/watch?v=GW0rj4sNH2w" class="link" target="_blank">JSConfUS 2013</a>, <strong>Facebook introduced a new library</strong> - React - with a <strong>radically different approach</strong> to the templating problem that <strong>lifted quite a few eyebrows</strong>.</p>
<p>Then at <a href="https://www.youtube.com/watch?v=x7cQ3mrcKaY" class="link" target="_blank">JSConfEU 2013</a> they gave <strong>more details</strong>, which made people <strong>even more skeptic</strong>.</p>
</div></section>
<section class="slide" data-pos="4-1-4">
<span class="pos">4-1-4</span>
<div class="slidecontent"><p>So a React app is made up by <strong>components</strong>. They are <strong>functions</strong> which you <strong>feed data</strong>,
called <strong>props</strong> in React lingo, and you <strong>get DOM back</strong>.</p>
</div></section>
<section class="slide question" data-pos="4-1-5">
<span class="pos">4-1-5</span>
<div class="slidecontent">
<p>Ok, so a React component <strong>serves the same purpose</strong> as a traditional template. Then what
is the fuss about? <strong>What is different</strong> about React?</p>
</div></section>
<section class="slide answer" data-pos="4-1-6">
<span class="pos">4-1-6</span>
<div class="slidecontent">
<p>Many things;</p>
<ul>
<li>We <strong>express the UI in JS</strong> instead of HTML</li>
<li>We <strong>rerender the whole UI on every update</strong> (what‽)</li>
<li>Components are <strong>inherently composable</strong></li>
</ul>
</div></section>
<section class="slide" data-pos="4-1-7">
<span class="pos">4-1-7</span>
<div class="slidecontent"><p>We'll <strong>take a look</strong> at these differences, and more, in the upcoming sections!</p>
</div></section>
</section>
<section>
<section class="slide sectiontitle">
<div class="slidecontent">
<div class='sectioncount'>Section 2/7</div>
<h3>Nested components</h3>
<p>Matryoshka time!</p>
</div>
</section>
<section class="slide" data-pos="4-2-1">
<span class="pos">4-2-1</span>
<div class="slidecontent"><p>React Apps are <strong>trees</strong> of components.</p>
</div></section>
<section class="slide" data-pos="4-2-2">
<span class="pos">4-2-2</span>
<div class="slidecontent"><p>We can <strong>use components within components</strong>.</p>
<p>This sounds banal, but the <strong>composability</strong> that follows from this is a <strong>huge advantage</strong> of React.</p>
</div></section>
<section class="slide" data-pos="4-2-3">
<span class="pos">4-2-3</span>
<div class="slidecontent"><p>As an example, let's say we've made <strong>components</strong> for the three <strong>sections of a news site</strong>:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> Topbar = <span class="hljs-function"><span class="hljs-params">props</span> =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">h2</span>></span>The Superhero Tattler<span class="hljs-tag"></<span class="hljs-name">h2</span>></span></span>;
);
<span class="hljs-keyword">let</span> Main = <span class="hljs-function"><span class="hljs-params">props</span> =></span> (
<span class="hljs-keyword">return</span> <span class="hljs-comment">// lots of stuff to generate the main section;</span>
);
<span class="hljs-keyword">let</span> Footer = <span class="hljs-function"><span class="hljs-params">props</span> =></span> (
<span class="hljs-keyword">return</span> <span class="xml"><span class="hljs-tag"><<span class="hljs-name">div"</span>></span>© The Tattler 2016<span class="hljs-tag"></<span class="hljs-name">div</span>></span></span>;
);
</code></pre>
</div></section>
<section class="slide" data-pos="4-2-4">
<span class="pos">4-2-4</span>
<div class="slidecontent"><p>We can now <strong>use these components</strong> in an all-encompassing <strong><code>Site</code> component</strong>:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> Site = <span class="hljs-function"><span class="hljs-params">props</span> =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>
<span class="hljs-tag"><<span class="hljs-name">Topbar</span>/></span>
<span class="hljs-tag"><<span class="hljs-name">Main</span>/></span>
<span class="hljs-tag"><<span class="hljs-name">Footer</span>/></span>
<span class="hljs-tag"></<span class="hljs-name">div</span>></span></span>
);
</code></pre>
<p>You can try this example in the <a href="resources/site/demos/nestedcomponents/index.html" target="_blank">Nested components</a> demo.</p>
</div></section>
<section class="slide" data-pos="4-2-5">
<span class="pos">4-2-5</span>
<div class="slidecontent"><p>Our <code>Site</code> as a tree:</p>
<p><img src="resources/4-2-5-23.svg" alt="dot"></p>
</div></section>
<section class="slide question" data-pos="4-2-6">
<span class="pos">4-2-6</span>
<div class="slidecontent">
<p>How can JSX <strong>tell the difference between an HTML element and a component</strong>?</p>
<pre><code><span class="hljs-keyword">let</span> output1 = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">Topbar</span>/></span></span>; <span class="hljs-comment">// Here we mean a component</span>
<span class="hljs-keyword">let</span> output2 = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>/></span></span>; <span class="hljs-comment">// Here we mean a regular HTML div element</span>
</code></pre></div></section>
<section class="slide answer" data-pos="4-2-7">
<span class="pos">4-2-7</span>
<div class="slidecontent">
<p>It is ridiculously simple - if the <strong>name is lower case</strong>, it is assumed to be a <strong>DOM tag</strong>, </p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> output1 = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>/></span></span>; <span class="hljs-comment">// --> React.createElement("div");</span>
</code></pre>
<p>While <strong>upper case</strong> means a <strong>component</strong> which has to be an actual name in your code.</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> output2 = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">Div</span>/></span></span>; <span class="hljs-comment">// --> React.createElement(Div);</span>
</code></pre>
</div></section>
</section>
<section>
<section class="slide sectiontitle">
<div class="slidecontent">
<div class='sectioncount'>Section 3/7</div>
<h3>Walk-through 1</h3>
<p>Building an organization</p>
</div>
</section>
<section class="slide" data-pos="4-3-1">
<span class="pos">4-3-1</span>
<div class="slidecontent"><p>We can start with empty file</p>
<pre><code class="lang-javascript">
</code></pre>
</div></section>
<section class="slide" data-pos="4-3-2">
<span class="pos">4-3-2</span>
<div class="slidecontent"><p>We start by importing <code>React</code></p>
<pre><code class="lang-javascript"><span class="hljs-keyword">import</span> React <span class="hljs-keyword">from</span> <span class="hljs-string">'react'</span>;
</code></pre>
</div></section>
<section class="slide" data-pos="4-3-3">
<span class="pos">4-3-3</span>
<div class="slidecontent"><p>How we use a react component</p>
<pre><code class="lang-javascript"><Organization />
</code></pre>
</div></section>
<section class="slide" data-pos="4-3-4">
<span class="pos">4-3-4</span>
<div class="slidecontent"><p>Defining our first component:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Organization = <span class="hljs-function"><span class="hljs-params">()</span> =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">h1</span>></span>Our Organization<span class="hljs-tag"></<span class="hljs-name">h1</span>></span></span>
);
<span class="hljs-keyword">export</span> <span class="hljs-keyword">default</span> Organization;
</code></pre>
</div></section>
<section class="slide" data-pos="4-3-5">
<span class="pos">4-3-5</span>
<div class="slidecontent"><p>Rendering our first component:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">import</span> React <span class="hljs-keyword">from</span> <span class="hljs-string">'react'</span>;
<span class="hljs-keyword">import</span> ReactDOM <span class="hljs-keyword">from</span> <span class="hljs-string">'react-dom'</span>;
<span class="hljs-keyword">import</span> Organization <span class="hljs-keyword">from</span> <span class="hljs-string">'./Organization'</span>;
ReactDOM.render(<span class="xml"><span class="hljs-tag"><<span class="hljs-name">Organization</span>/></span></span>, <span class="hljs-built_in">document</span>.getElementById(<span class="hljs-string">'root'</span>));
</code></pre>
</div></section>
<section class="slide" data-pos="4-3-6">
<span class="pos">4-3-6</span>
<div class="slidecontent"><p>Our <strong>mount point</strong> in <code>index.html</code>:</p>
<pre><code class="lang-html"> <span class="hljs-tag"><<span class="hljs-name">div</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"root"</span>></span><span class="hljs-tag"></<span class="hljs-name">div</span>></span>
</code></pre>
</div></section>
<section class="slide" data-pos="4-3-7">
<span class="pos">4-3-7</span>
<div class="slidecontent"><p>Looking at the Devtools:
<img src="resources/images/devtools.png" alt="Devtools"></p>
</div></section>
<section class="slide" data-pos="4-3-8">
<span class="pos">4-3-8</span>
<div class="slidecontent"><p>Transpiling a component:
<img src="resources/images/component_repl.png" alt="Babel Repl"></p>
<p><a href="https://babeljs.io/repl/#?babili=false&browsers=&build=&builtIns=false&spec=false&loose=false&code_lz=MYewdgzgLgBA8gJwOYEMwEsBeKrvDAXhgAoBKQgPhICgYYAeACwEYK4BXBeZNLHPMPQD0LCtVIBuatXqJUGbLnBCKQA&debug=false&forceAllTransforms=false&shippedProposals=false&circleciRepo=&evaluate=false&fileSize=false&sourceType=module&lineWrap=true&presets=es2015%2Creact%2Cstage-2&prettier=false&targets=&version=6.26.0&envVersion=">Babel Repl</a></p>
</div></section>
<section class="slide" data-pos="4-3-9">
<span class="pos">4-3-9</span>
<div class="slidecontent"><p>Starting our <strong>tree</strong> of components</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">import</span> React <span class="hljs-keyword">from</span> <span class="hljs-string">'react'</span>;
<span class="hljs-keyword">import</span> Organization <span class="hljs-keyword">from</span> <span class="hljs-string">'./Organization.js'</span>;
<span class="hljs-keyword">const</span> App = <span class="hljs-function"><span class="hljs-params">()</span> =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>
<span class="hljs-tag"><<span class="hljs-name">Organization</span>/></span>
<span class="hljs-tag"></<span class="hljs-name">div</span>></span></span>
);
<span class="hljs-keyword">export</span> <span class="hljs-keyword">default</span> App;
</code></pre>
<pre><code class="lang-javascript">ReactDOM.render(<span class="xml"><span class="hljs-tag"><<span class="hljs-name">App</span>/></span></span>, <span class="hljs-built_in">document</span>.getElementById(<span class="hljs-string">'root'</span>));
</code></pre>
</div></section>
<section class="slide" data-pos="4-3-10">
<span class="pos">4-3-10</span>
<div class="slidecontent"><p>Rendering some input <strong>props</strong></p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Organization = <span class="hljs-function">(<span class="hljs-params">props</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">h1</span>></span>{props.name} Organization<span class="hljs-tag"></<span class="hljs-name">h1</span>></span></span>
);
</code></pre>
<p>Passing in a <code>name</code> prop</p>
<pre><code class="lang-javascript"> <Organization name=<span class="hljs-string">"Stephen's"</span>/>
</code></pre>
</div></section>
<section class="slide" data-pos="4-3-11">
<span class="pos">4-3-11</span>
<div class="slidecontent"><p>Self documenting props via <strong>destructuring</strong></p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Organization = <span class="hljs-function">(<span class="hljs-params">{name}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">h1</span>></span>{name} Organization<span class="hljs-tag"></<span class="hljs-name">h1</span>></span></span>
);
</code></pre>
<pre><code class="lang-javascript"> <Organization name=<span class="hljs-string">"Stephen's"</span>/>
</code></pre>
</div></section>
<section class="slide" data-pos="4-3-12">
<span class="pos">4-3-12</span>
<div class="slidecontent"><p>Creating a group component:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">import</span> React <span class="hljs-keyword">from</span> <span class="hljs-string">'react'</span>;
<span class="hljs-keyword">const</span> Group = <span class="hljs-function">(<span class="hljs-params">{name}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">h2</span>></span>Group {name}<span class="hljs-tag"></<span class="hljs-name">h2</span>></span></span>
);
<span class="hljs-keyword">export</span> <span class="hljs-keyword">default</span> Group;
</code></pre>
</div></section>
<section class="slide" data-pos="4-3-13">
<span class="pos">4-3-13</span>
<div class="slidecontent"><p>Adding to the Organization component:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Organization = <span class="hljs-function">(<span class="hljs-params">{name}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">h1</span>></span>{name} Organization<span class="hljs-tag"></<span class="hljs-name">h1</span>></span></span>,
<Group/>
);
</code></pre>
</div></section>
<section class="slide question" data-pos="4-3-14">
<span class="pos">4-3-14</span>
<div class="slidecontent">
<p>We can't return two things from a function or lambda, so what options do we have?</p>
</div></section>
<section class="slide answer" data-pos="4-3-15">
<span class="pos">4-3-15</span>
<div class="slidecontent">
<p>Wrap in a div.</p>
<pre><code class="lang-html"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>
<span class="hljs-tag"><<span class="hljs-name">Item</span>/></span>
<span class="hljs-tag"><<span class="hljs-name">OtherItem</span>/></span>
<span class="hljs-tag"></<span class="hljs-name">div</span>></span>
</code></pre>
</div></section>
<section class="slide answer" data-pos="4-3-16">
<span class="pos">4-3-16</span>
<div class="slidecontent">
<p>Wrap in a fragment:</p>
<pre><code class="lang-javascript"><React.Fragment>
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">Item</span>/></span></span>
<OtherItem/>
<span class="xml"><span class="hljs-tag"></<span class="hljs-name">React.Fragment</span>></span></span>
</code></pre>
</div></section>
<section class="slide answer" data-pos="4-3-17">
<span class="pos">4-3-17</span>
<div class="slidecontent">
<p>Import as <code>F</code>:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">import</span> React, {Fragment <span class="hljs-keyword">as</span> F} <span class="hljs-keyword">from</span> <span class="hljs-string">'react'</span>;
<span class="hljs-keyword">import</span> Group <span class="hljs-keyword">from</span> <span class="hljs-string">'./Group'</span>;
<span class="hljs-keyword">const</span> Organization = <span class="hljs-function">(<span class="hljs-params">{name}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">F</span>></span>
<span class="hljs-tag"><<span class="hljs-name">h1</span>></span>{name} Organization<span class="hljs-tag"></<span class="hljs-name">h1</span>></span>
<span class="hljs-tag"><<span class="hljs-name">Group</span> <span class="hljs-attr">name</span>=<span class="hljs-string">"Engineering"</span>/></span>
<span class="hljs-tag"></<span class="hljs-name">F</span>></span>
);</span>
</code></pre>
</div></section>
<section class="slide answer" data-pos="4-3-18">
<span class="pos">4-3-18</span>
<div class="slidecontent">
<p>Fragment shorthand syntax:</p>
<pre><code class="lang-javascript"><>
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">Item</span>/></span></span>
<OtherItem/>
<span class="xml"><span class="hljs-tag"></></span></span>
</code></pre>
</div></section>
<section class="slide answer" data-pos="4-3-19">
<span class="pos">4-3-19</span>
<div class="slidecontent">
<p>Return an array</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Organization = <span class="hljs-function">(<span class="hljs-params">{name}</span>) =></span> [
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">h1</span>></span>{name} Organization<span class="hljs-tag"></<span class="hljs-name">h1</span>></span></span>,
<Group name=<span class="hljs-string">"Engineering"</span>/>
];
</code></pre>
</div></section>
</section>
<section>
<section class="slide sectiontitle">
<div class="slidecontent">
<div class='sectioncount'>Section 4/7</div>
<h3>Exercise 1</h3>
<p>Adding Users</p>
</div>
</section>
<section class="slide" data-pos="4-4-1">
<span class="pos">4-4-1</span>
<div class="slidecontent"><h2 id="thou-shalt-">Thou shalt:</h2>
<ol>
<li>Create a <code>User</code> component.</li>
<li>Add 2 <code>User</code>s to the group component<ul>
<li>Use <code>Fragment</code> to return the <code>h2</code> + 2 <code>User</code>s from group.</li>
<li>Pass in <code>id</code> and <code>name</code> to users.<ul>
<li><code>id</code> shall be a number.</li>
</ul>
</li>
</ul>
</li>
</ol>
</div></section>
</section>
<section>
<section class="slide sectiontitle">
<div class="slidecontent">
<div class='sectioncount'>Section 5/7</div>
<h3>JSX Basics</h3>
<p>Waiter, there's HTML in my JS!</p>
</div>
</section>
<section class="slide" data-pos="4-5-1">
<span class="pos">4-5-1</span>
<div class="slidecontent"><p>As the previous section taught us, <strong>JSX</strong> is a <strong>light syntactic sugar</strong> aiming to make it <strong>easier to express nested data structures</strong> with JavaScript. Let's explore how it works!</p>
</div></section>
<section class="slide" data-pos="4-5-2">
<span class="pos">4-5-2</span>
<div class="slidecontent"><p>We keep saying the <strong>syntax is simple</strong>, but, <strong>how exactly do we use it</strong>?</p>
<p>Well - we <strong>enter JSX mode</strong> simply by <strong>opening a tag</strong>. If you <strong>close the (last) tag</strong> then you are <strong>back in JS mode</strong> again.</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> License = <span class="hljs-function"><span class="hljs-params">()</span>=></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">p</span>></span>Steal this and we'll <span class="hljs-tag"><<span class="hljs-name">em</span>></span>SMACK YOU SILLY<span class="hljs-tag"></<span class="hljs-name">em</span>></span>!<span class="hljs-tag"></<span class="hljs-name">p</span>></span></span>
);
</code></pre>
</div></section>
<section class="slide" data-pos="4-5-3">
<span class="pos">4-5-3</span>
<div class="slidecontent"><p>If we want to <strong>go to JS</strong> from <strong>inside JSX</strong> mode, we use curly braces:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> msg = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">span</span>></span>Hello, {target || 'mate'}!<span class="hljs-tag"></<span class="hljs-name">span</span>></span></span>;
</code></pre>
</div></section>
<section class="slide" data-pos="4-5-4">
<span class="pos">4-5-4</span>
<div class="slidecontent"><p>Thus the <strong>map</strong> for <strong>traveling between JS and JSX</strong> could be described like this:</p>
<p><img src="resources/4-5-4-85.svg" alt="dot"></p>
</div></section>
<section class="slide" data-pos="4-5-5">
<span class="pos">4-5-5</span>
<div class="slidecontent"><p>Although note that this can be <strong>nested to any depth</strong>:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> output = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>{<span class="hljs-tag"><<span class="hljs-name">div</span>></span>{<span class="hljs-tag"><<span class="hljs-name">div</span>></span>{"Inception!"}<span class="hljs-tag"></<span class="hljs-name">div</span>></span>}<span class="hljs-tag"></<span class="hljs-name">div</span>></span>}<span class="hljs-tag"></<span class="hljs-name">div</span>></span></span>;
</code></pre>
</div></section>
</section>
<section>
<section class="slide sectiontitle">
<div class="slidecontent">
<div class='sectioncount'>Section 6/7</div>
<h3>Translation issues</h3>
<p>English to French to English shenanigans</p>
</div>
</section>
<section class="slide" data-pos="4-6-1">
<span class="pos">4-6-1</span>
<div class="slidecontent"><p>When we "<strong>send JS into JSX</strong>" using curly braces...</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> output = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>{someValue}<span class="hljs-tag"></<span class="hljs-name">div</span>></span></span>;
</code></pre>
<p>...what can we send, and <strong>how is it interpreted</strong>?</p>
</div></section>
<section class="slide" data-pos="4-6-2">
<span class="pos">4-6-2</span>
<div class="slidecontent"><p>Here's what!</p>
<p><strong>Strings</strong> or <strong>numbers</strong> end up as <strong>text nodes</strong>, as we've seen many times already:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> name = <span class="hljs-string">'Steve'</span>, number = <span class="hljs-number">5</span>;
<span class="hljs-keyword">let</span> output = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>My friend {name} has {number} bottles of beer<span class="hljs-tag"></<span class="hljs-name">div</span>></span></span>;
<span class="hljs-comment">// --> "<div>My friend Steve has 5 bottles of beer</div>"</span>
</code></pre>
<p><strong>Earlier versions</strong> of React put a <strong><code>span</code> around the strings</strong>, but that <strong>doesn't happen anymore</strong>.</p>
</div></section>
<section class="slide" data-pos="4-6-3">
<span class="pos">4-6-3</span>
<div class="slidecontent"><p><strong>JSX</strong> elements are passed straight through:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> friend = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">strong</span>></span>Steve<span class="hljs-tag"></<span class="hljs-name">strong</span>></span></span>;
<span class="hljs-keyword">let</span> output = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>My friend {friend} is thirsty<span class="hljs-tag"></<span class="hljs-name">div</span>></span></span>;
<span class="hljs-comment">// --> "<div>My friend <strong>Steve</strong> is thirsty</div>"</span>
</code></pre>
</div></section>
<section class="slide" data-pos="4-6-4">
<span class="pos">4-6-4</span>
<div class="slidecontent"><p><strong><code>undefined</code>, <code>null</code> and <code>false</code></strong> don't create anything:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> favourite = <span class="hljs-literal">null</span>;
<span class="hljs-keyword">let</span> output = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>Steve's favourite meal: {favourite}<span class="hljs-tag"></<span class="hljs-name">div</span>></span></span>;
<span class="hljs-comment">// --> "<div>Steve's favourite meal: </div>"</span>
</code></pre>
<p>Curiously, <strong>neither does <code>true</code> or functions</strong>.</p>
</div></section>
<section class="slide" data-pos="4-6-5">
<span class="pos">4-6-5</span>
<div class="slidecontent"><p>Items in an <strong>array</strong> will be <strong>interpreted individually</strong> (with no space in-between):</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">let</span> numbers = [<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>];
<span class="hljs-keyword">let</span> output = <span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>Steve can count: {numbers} bottles of beer<span class="hljs-tag"></<span class="hljs-name">div</span>></span></span>
<span class="hljs-comment">// --> "<div>Steve can count: 123 bottles of beer</div>"</span>
</code></pre>
</div></section>
<section class="slide" data-pos="4-6-6">
<span class="pos">4-6-6</span>
<div class="slidecontent"><p>And finally, for completion's sake</p>
<ul>
<li>an <strong>object</strong> throws an <strong>error</strong></li>
<li><code>NaN</code> renders the string <code>"NaN"</code>.</li>
</ul>
</div></section>
</section>
<section>
<section class="slide sectiontitle">
<div class="slidecontent">
<div class='sectioncount'>Section 7/7</div>
<h3>Walk-through 1B</h3>
<p>Building an organization</p>
</div>
</section>
<section class="slide" data-pos="4-7-1">
<span class="pos">4-7-1</span>
<div class="slidecontent"><p>After Exercise 1 <code>User.js</code>:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">import</span> React <span class="hljs-keyword">from</span> <span class="hljs-string">'react'</span>;
<span class="hljs-keyword">const</span> User = <span class="hljs-function">(<span class="hljs-params">{name, id}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">h3</span>></span>Name: {name}, id: {id}<span class="hljs-tag"></<span class="hljs-name">h3</span>></span></span>
);
<span class="hljs-keyword">export</span> <span class="hljs-keyword">default</span> User;
</code></pre>
</div></section>
<section class="slide" data-pos="4-7-2">
<span class="pos">4-7-2</span>
<div class="slidecontent"><p>After Exercise 1 <code>Group.js</code>:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">import</span> React, {Fragment <span class="hljs-keyword">as</span> F} <span class="hljs-keyword">from</span> <span class="hljs-string">'react'</span>;
<span class="hljs-keyword">import</span> User <span class="hljs-keyword">from</span> <span class="hljs-string">'./User'</span>;
<span class="hljs-keyword">const</span> Group = <span class="hljs-function">(<span class="hljs-params">{name}</span>) =></span> (
<F>
<h2>Group {name}</h2>
<User name="Stephen" id={123}/>
<User name="David" id={456}/>
</F>
);
export default Group;
</code></pre>
</div></section>
<section class="slide" data-pos="4-7-3">
<span class="pos">4-7-3</span>
<div class="slidecontent"><p>Dealing with a dynamic array of users:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Group = <span class="hljs-function">(<span class="hljs-params">{name, users}</span>) =></span> (
</code></pre>
</div></section>
<section class="slide" data-pos="4-7-4">
<span class="pos">4-7-4</span>
<div class="slidecontent"><p>Providing the array:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Organization = <span class="hljs-function">(<span class="hljs-params">{name}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">F</span>></span>
<span class="hljs-tag"><<span class="hljs-name">h1</span>></span>{name} Organization<span class="hljs-tag"></<span class="hljs-name">h1</span>></span>
<span class="hljs-tag"><<span class="hljs-name">Group</span>
<span class="hljs-attr">name</span>=<span class="hljs-string">"Engineering"</span>
<span class="hljs-attr">users</span>=<span class="hljs-string">{[</span>
{
<span class="hljs-attr">name:</span> "<span class="hljs-attr">Stephen</span>",
<span class="hljs-attr">id:</span> <span class="hljs-attr">123</span>
},
{
<span class="hljs-attr">name:</span> "<span class="hljs-attr">David</span>",
<span class="hljs-attr">id:</span> <span class="hljs-attr">456</span>
}
]}
/></span>
<span class="hljs-tag"></<span class="hljs-name">F</span>></span>
);</span>
</code></pre>
</div></section>
<section class="slide" data-pos="4-7-5">
<span class="pos">4-7-5</span>
<div class="slidecontent"><p>Rendering the array:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Group = <span class="hljs-function">(<span class="hljs-params">{name, users}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">F</span>></span>
<span class="hljs-tag"><<span class="hljs-name">h2</span>></span>Group {name}<span class="hljs-tag"></<span class="hljs-name">h2</span>></span>
{
users.map(user => (
<span class="hljs-tag"><<span class="hljs-name">User</span> <span class="hljs-attr">name</span>=<span class="hljs-string">{user.name}</span> <span class="hljs-attr">id</span>=<span class="hljs-string">{user.id}/</span>></span>
))
}
<span class="hljs-tag"></<span class="hljs-name">F</span>></span>
);</span>
</code></pre>
</div></section>
<section class="slide" data-pos="4-7-6">
<span class="pos">4-7-6</span>
<div class="slidecontent"><p>Remove repetition with spread syntax:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Group = <span class="hljs-function">(<span class="hljs-params">{name, users}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">F</span>></span>
<span class="hljs-tag"><<span class="hljs-name">h2</span>></span>Group {name}<span class="hljs-tag"></<span class="hljs-name">h2</span>></span>
{
users.map(user => (
<span class="hljs-tag"><<span class="hljs-name">User</span> {<span class="hljs-attr">...user</span>}/></span>
))
}
<span class="hljs-tag"></<span class="hljs-name">F</span>></span>
);</span>
</code></pre>
</div></section>
<section class="slide" data-pos="4-7-7">
<span class="pos">4-7-7</span>
<div class="slidecontent"><p><img src="resources/images/key-warning.png" alt="key warning"></p>
</div></section>
<section class="slide" data-pos="4-7-8">
<span class="pos">4-7-8</span>
<div class="slidecontent"><p>Fixing the key warning:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Group = <span class="hljs-function">(<span class="hljs-params">{name, users}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">F</span>></span>
<span class="hljs-tag"><<span class="hljs-name">h2</span>></span>Group {name}<span class="hljs-tag"></<span class="hljs-name">h2</span>></span>
{
users.map((user, index)=> (
<span class="hljs-tag"><<span class="hljs-name">User</span> {<span class="hljs-attr">...user</span>} <span class="hljs-attr">key</span>=<span class="hljs-string">{index}/</span>></span>
))
}
<span class="hljs-tag"></<span class="hljs-name">F</span>></span>
);</span>
</code></pre>
</div></section>
<section class="slide" data-pos="4-7-9">
<span class="pos">4-7-9</span>
<div class="slidecontent"><p>Using <code>id</code> as key:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Group = <span class="hljs-function">(<span class="hljs-params">{name, users}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">F</span>></span>
<span class="hljs-tag"><<span class="hljs-name">h2</span>></span>Group {name}<span class="hljs-tag"></<span class="hljs-name">h2</span>></span>
{
users.map((user, index)=> (
<span class="hljs-tag"><<span class="hljs-name">User</span> {<span class="hljs-attr">...user</span>} <span class="hljs-attr">key</span>=<span class="hljs-string">{user.id}/</span>></span>
))
}
<span class="hljs-tag"></<span class="hljs-name">F</span>></span>
);</span>
</code></pre>
</div></section>
<section class="slide" data-pos="4-7-10">
<span class="pos">4-7-10</span>
<div class="slidecontent"><p>Passing in an <strong>optional</strong> avatar:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> Organization = <span class="hljs-function">(<span class="hljs-params">{name}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">F</span>></span>
<span class="hljs-tag"><<span class="hljs-name">h1</span>></span>{name} Organization<span class="hljs-tag"></<span class="hljs-name">h1</span>></span>
<span class="hljs-tag"><<span class="hljs-name">Group</span>
<span class="hljs-attr">name</span>=<span class="hljs-string">"Engineering"</span>
<span class="hljs-attr">users</span>=<span class="hljs-string">{[</span>
{
<span class="hljs-attr">name:</span> "<span class="hljs-attr">Stephen</span>", <span class="hljs-attr">id:</span> <span class="hljs-attr">123</span>,
<span class="hljs-attr">avatar:</span> "<span class="hljs-attr">http:</span>//<span class="hljs-attr">via.placeholder.com</span>/<span class="hljs-attr">150x150</span>"
},
{ <span class="hljs-attr">name:</span> "<span class="hljs-attr">David</span>", <span class="hljs-attr">id:</span> <span class="hljs-attr">456</span> }
]}
/></span>
<span class="hljs-tag"></<span class="hljs-name">F</span>></span>
);</span>
</code></pre>
</div></section>
<section class="slide" data-pos="4-7-11">
<span class="pos">4-7-11</span>
<div class="slidecontent"><p>Conditional rendering:</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> User = <span class="hljs-function">(<span class="hljs-params">{name, id, avatar}</span>) =></span> (
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">F</span>></span>
<span class="hljs-tag"><<span class="hljs-name">h3</span>></span>Name: {name}, id: {id}<span class="hljs-tag"></<span class="hljs-name">h3</span>></span>
{ avatar
? <span class="hljs-tag"><<span class="hljs-name">img</span> <span class="hljs-attr">src</span>=<span class="hljs-string">{avatar}/</span>></span>
: "No Avatar :("
}
<span class="hljs-tag"></<span class="hljs-name">F</span>></span>
);</span>
</code></pre>
</div></section>
<section class="slide question" data-pos="4-7-12">
<span class="pos">4-7-12</span>
<div class="slidecontent">
<p>Can we have if statements?</p>
</div></section>
<section class="slide answer" data-pos="4-7-13">
<span class="pos">4-7-13</span>
<div class="slidecontent">
<p>No</p>
<ul>
<li><a href="https://babeljs.io/repl/#?babili=false&browsers=&build=&builtIns=false&spec=false&loose=false&code_lz=MYewdgzgLgBAqhApgJxgXhgCgN5gIYC2iANDAJYAmpeAbnlHsgL4CU6AfFgFAwwA8AMXY9e_ABYBmdgDlCiAFwxccpqUqLslJnwD0k4aKUxa9RiMMB-fmQIBzGBGTA02Ew2Y6DhmIoBE0kBgAQTp3H0xfcxgmEV0hLhYAbi4uPgQUTyA&debug=false&forceAllTransforms=false&shippedProposals=false&circleciRepo=&evaluate=false&fileSize=false&sourceType=module&lineWrap=true&presets=es2015%2Creact%2Cstage-2&prettier=false&targets=&version=6.26.0&envVersion=">With ternary</a></li>
<li><a href="https://babeljs.io/repl/#?babili=false&browsers=&build=&builtIns=false&spec=false&loose=false&code_lz=MYewdgzgLgBAqhApgJxgXhgCgN5gIYC2iANDAJYAmpeAbnlHsgL4CU6AfFgFAwwA8AMXY9e_ABYBmdgDlCiAFwxccpqUqLslJnwD0k4aKUwRhsgDNMteozbYTh_mQIBzGBGTA02Kw2Y6DDkwwiAA2SEr2hgBE0iAwAIJ0vjDymFGRMEz2Wby6QlwsANxcXHwIKP5AA&debug=false&forceAllTransforms=false&shippedProposals=false&circleciRepo=&evaluate=false&fileSize=false&sourceType=module&lineWrap=true&presets=es2015%2Creact%2Cstage-2&prettier=false&targets=&version=6.26.0&envVersion=">With if</a></li>
</ul>
</div></section>
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