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<!DOCTYPE html>
<html>
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<title>React | Displaying Data</title>
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Displaying Data
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JSX in Depth
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<a href="/react/tips/style-props-value-px.html">Shorthand for Specifying Pixel Values in style props</a>
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<a href="/react/tips/children-props-type.html">Type of the Children props</a>
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<a href="/react/tips/controlled-input-null-value.html">Value of null for Controlled Input</a>
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<a href="/react/tips/props-in-getInitialState-as-anti-pattern.html">Props in getInitialState Is an Anti-Pattern</a>
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<a href="/react/tips/dom-event-listeners.html">DOM Event Listeners in a Component</a>
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<a href="/react/tips/initial-ajax.html">Load Initial Data via AJAX</a>
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<a href="/react/tips/false-in-jsx.html">False in JSX</a>
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<a href="/react/tips/communicate-between-components.html">Communicate Between Components</a>
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<div class="inner-content">
<h1>Displaying Data</h1>
<div class="subHeader"></div>
<p>The most basic thing you can do with a UI is display some data. React makes it easy to display data and automatically keeps the interface up-to-date when the data changes.</p>
<h2><a class="anchor" name="getting-started"></a>Getting Started <a class="hash-link" href="#getting-started">#</a></h2>
<p>Let&#39;s look at a really simple example. Create a <code>hello-react.html</code> file with the following code:</p>
<div class="highlight"><pre><code class="html language-html" data-lang="html"><span class="cp">&lt;!DOCTYPE html&gt;</span>
<span class="nt">&lt;html&gt;</span>
<span class="nt">&lt;head&gt;</span>
<span class="nt">&lt;title&gt;</span>Hello React<span class="nt">&lt;/title&gt;</span>
<span class="nt">&lt;script </span><span class="na">src=</span><span class="s">&quot;http://fb.me/react-0.8.0.min.js&quot;</span><span class="nt">&gt;&lt;/script&gt;</span>
<span class="nt">&lt;script </span><span class="na">src=</span><span class="s">&quot;http://fb.me/JSXTransformer-0.8.0.js&quot;</span><span class="nt">&gt;&lt;/script&gt;</span>
<span class="nt">&lt;/head&gt;</span>
<span class="nt">&lt;body&gt;</span>
<span class="nt">&lt;div</span> <span class="na">id=</span><span class="s">&quot;example&quot;</span><span class="nt">&gt;&lt;/div&gt;</span>
<span class="nt">&lt;script </span><span class="na">type=</span><span class="s">&quot;text/jsx&quot;</span><span class="nt">&gt;</span>
<span class="c1">// ** Your code goes here! **</span>
<span class="nt">&lt;/script&gt;</span>
<span class="nt">&lt;/body&gt;</span>
<span class="nt">&lt;/html&gt;</span>
</code></pre></div>
<p>For the rest of the documentation, we&#39;ll just focus on the JavaScript code and assume it&#39;s inserted into a template like the one above. Replace the placeholder comment above with the following JS:</p>
<div class="highlight"><pre><code class="javascript language-javascript" data-lang="javascript"><span class="cm">/** @jsx React.DOM */</span>
<span class="kd">var</span> <span class="nx">HelloWorld</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span>
<span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
<span class="k">return</span> <span class="p">(</span>
<span class="o">&lt;</span><span class="nx">p</span><span class="o">&gt;</span>
<span class="nx">Hello</span><span class="p">,</span> <span class="o">&lt;</span><span class="nx">input</span> <span class="nx">type</span><span class="o">=</span><span class="s2">&quot;text&quot;</span> <span class="nx">placeholder</span><span class="o">=</span><span class="s2">&quot;Your name here&quot;</span> <span class="o">/&gt;!</span>
<span class="nx">It</span> <span class="nx">is</span> <span class="p">{</span><span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">date</span><span class="p">.</span><span class="nx">toTimeString</span><span class="p">()}</span>
<span class="o">&lt;</span><span class="err">/p&gt;</span>
<span class="p">);</span>
<span class="p">}</span>
<span class="p">});</span>
<span class="nx">setInterval</span><span class="p">(</span><span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
<span class="nx">React</span><span class="p">.</span><span class="nx">renderComponent</span><span class="p">(</span>
<span class="o">&lt;</span><span class="nx">HelloWorld</span> <span class="nx">date</span><span class="o">=</span><span class="p">{</span><span class="k">new</span> <span class="nb">Date</span><span class="p">()}</span> <span class="o">/&gt;</span><span class="p">,</span>
<span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">&#39;example&#39;</span><span class="p">)</span>
<span class="p">);</span>
<span class="p">},</span> <span class="mi">500</span><span class="p">);</span>
</code></pre></div><h2><a class="anchor" name="reactive-updates"></a>Reactive Updates <a class="hash-link" href="#reactive-updates">#</a></h2>
<p>Open <code>hello-react.html</code> in a web browser and type your name into the text field. Notice that React is only changing the time string in the UI — any input you put in the text field remains, even though you haven&#39;t written any code to manage this behavior. React figures it out for you and does the right thing.</p>
<p>The way we are able to figure this out is that React does not manipulate the DOM unless it needs to. <strong>It uses a fast, internal mock DOM to perform diffs and computes the most efficient DOM mutation for you.</strong></p>
<p>The inputs to this component are called <code>props</code> — short for &quot;properties&quot;. They&#39;re passed as attributes in JSX syntax. You should think of these as immutable within the component, that is, <strong>never write to <code>this.props</code></strong>.</p>
<h2><a class="anchor" name="components-are-just-like-functions"></a>Components are Just Like Functions <a class="hash-link" href="#components-are-just-like-functions">#</a></h2>
<p>React components are very simple. You can think of them as simple function that take in <code>props</code> and <code>state</code> (discussed later) and render HTML. Because they&#39;re so simple, it makes them very easy to reason about.</p>
<blockquote>
<p>Note:</p>
<p><strong>One limitation</strong>: React components can only render a single root node. If you want to return multiple nodes they <em>must</em> be wrapped in a single root.</p>
</blockquote>
<h2><a class="anchor" name="jsx-syntax"></a>JSX Syntax <a class="hash-link" href="#jsx-syntax">#</a></h2>
<p>We strongly believe that components are the right way to separate concerns rather than &quot;templates&quot; and &quot;display logic.&quot; We think that markup and the code that generates it are intimately tied together. Additionally, display logic is often very complex and using template languages to express it becomes cumbersome.</p>
<p>We&#39;ve found that the best solution for this problem is to generate markup directly from the JavaScript code such that you can use all of the expressive power of a real programming language to build UIs. In order to make this easier, we&#39;ve added a very simple, <strong>optional</strong> HTML-like syntax for the function calls that generate markup called JSX.</p>
<p><strong>JSX lets you write JavaScript function calls with HTML syntax.</strong> To generate a link in React using pure JavaScript you&#39;d write: <code>React.DOM.a({href: &#39;http://facebook.github.io/react/&#39;}, &#39;Hello React!&#39;)</code>. With JSX this becomes <code>&lt;a href=&quot;http://facebook.github.io/react/&quot;&gt;Hello React!&lt;/a&gt;</code>. We&#39;ve found this has made building React apps easier and designers tend to prefer the syntax, but everyone has their own workflow, so <strong>JSX is not required to use React.</strong></p>
<p>JSX is very small; the &quot;hello, world&quot; example above uses every feature of JSX. To learn more about it, see <a href="/react/docs/jsx-in-depth.html">JSX in depth</a>. Or see the transform in action in <a href="/react/jsx-compiler.html">our live JSX compiler</a>.</p>
<p>JSX is similar to HTML, but not exactly the same. See <a href="/react/docs/jsx-gotchas.html">JSX gotchas</a> for some key differences.</p>
<p>The easiest way to get started with JSX is to use the in-browser <code>JSXTransformer</code>. We strongly recommend that you don&#39;t use this in production. You can precompile your code using our command-line <a href="http://npmjs.org/package/react-tools">react-tools</a> package.</p>
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