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Dan Abramov
428 lines
16 KiB
HTML
428 lines
16 KiB
HTML
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<head>
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<meta charset="utf-8">
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<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
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<title>Hello World - React</title>
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<a class="nav-home" href="/react/">
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React
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<li><a href="/react/docs/hello-world.html" class="active">Docs</a></li>
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<a class="edit-page-link" href="https://github.com/facebook/react/tree/master/docs/docs/hello-world.md" target="_blank">Edit on GitHub</a>
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<h1>
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Hello World
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</h1>
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<div class="subHeader"></div>
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<p>The easiest way to get started with React is to use <a href="http://codepen.io/gaearon/pen/ZpvBNJ?editors=0010">this Hello World example code on CodePen</a>. You don't need to install anything; you can just open it in another tab and follow along as we go through examples. If you'd rather use a local development environment, check out the <a href="/react/docs/installation.html">Installation</a> page.</p>
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<p>The smallest React example looks like this:</p>
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<div class="highlight"><pre><code class="language-js" data-lang="js"><span class="nx">ReactDOM</span><span class="p">.</span><span class="nx">render</span><span class="p">(</span>
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<span class="o"><</span><span class="nx">h1</span><span class="o">></span><span class="nx">Hello</span><span class="p">,</span> <span class="nx">world</span><span class="o">!<</span><span class="err">/h1>,</span>
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<span class="nb">document</span><span class="p">.</span><span class="nx">getElementById</span><span class="p">(</span><span class="s1">'root'</span><span class="p">)</span>
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<span class="p">);</span>
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</code></pre></div>
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<p>It renders a header saying "Hello, world!" on the page.</p>
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<p>The next few sections will gradually introduce you to using React. We will examine the building blocks of React apps: elements and components. Once you master them, you can create complex apps from small reusable pieces.</p>
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<h2>A Note on JavaScript</h2>
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<p>React is a JavaScript library, and so it assumes you have a basic understanding of the JavaScript language. If you don't feel very confident, we recommend <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/A_re-introduction_to_JavaScript">refreshing your JavaScript knowledge</a> so you can follow along more easily.</p>
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<p>We also use some of the ES6 syntax in the examples. We try to use it sparingly because it's still relatively new, but we encourage you to get familiar with <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions">arrow functions</a>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes">classes</a>, <a href="https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Template_literals">template literals</a>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let"><code>let</code></a>, and <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/const"><code>const</code></a> statements. You can use <a href="http://babeljs.io/repl/#?babili=false&evaluate=true&lineWrap=false&presets=es2015%2Creact&experimental=false&loose=false&spec=false&code=const%20element%20%3D%20%3Ch1%3EHello%2C%20world!%3C%2Fh1%3E%3B%0Aconst%20container%20%3D%20document.getElementById('root')%3B%0AReactDOM.render(element%2C%20container)%3B%0A">Babel REPL</a> to check what ES6 code compiles to.</p>
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<div class="docs-prevnext">
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<a class="docs-prev" href="/react/docs/installation.html">← Prev</a>
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<a class="docs-next" href="/react/docs/introducing-jsx.html">Next →</a>
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<h3>Quick Start</h3>
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<li>
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<a href="/react/docs/installation.html">Installation</a>
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<a href="/react/docs/hello-world.html" class="active">Hello World</a>
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<a href="/react/docs/introducing-jsx.html">Introducing JSX</a>
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<a href="/react/docs/rendering-elements.html">Rendering Elements</a>
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<a href="/react/docs/components-and-props.html">Components and Props</a>
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<a href="/react/docs/state-and-lifecycle.html">State and Lifecycle</a>
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<a href="/react/docs/handling-events.html">Handling Events</a>
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<a href="/react/docs/conditional-rendering.html">Conditional Rendering</a>
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<a href="/react/docs/lists-and-keys.html">Lists and Keys</a>
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<a href="/react/docs/forms.html">Forms</a>
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<a href="/react/docs/lifting-state-up.html">Lifting State Up</a>
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<a href="/react/docs/composition-vs-inheritance.html">Composition vs Inheritance</a>
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</li>
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<li>
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<a href="/react/docs/thinking-in-react.html">Thinking In React</a>
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</ul>
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<div class="nav-docs-section">
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<h3>Advanced Guides</h3>
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<ul>
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<a href="/react/docs/jsx-in-depth.html">JSX In Depth</a>
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<li>
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<a href="/react/docs/typechecking-with-proptypes.html">Typechecking With PropTypes</a>
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<a href="/react/docs/refs-and-the-dom.html">Refs and the DOM</a>
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<a href="/react/docs/uncontrolled-components.html">Uncontrolled Components</a>
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<a href="/react/docs/optimizing-performance.html">Optimizing Performance</a>
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<a href="/react/docs/react-without-es6.html">React Without ES6</a>
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<a href="/react/docs/react-without-jsx.html">React Without JSX</a>
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<a href="/react/docs/reconciliation.html">Reconciliation</a>
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<a href="/react/docs/context.html">Context</a>
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<h3>Reference</h3>
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<a href="/react/docs/react-api.html">React</a>
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<a href="/react/docs/react-component.html">React.Component</a>
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<a href="/react/docs/react-dom.html">ReactDOM</a>
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<a href="/react/docs/javascript-environment-requirements.html">JS Environment Requirements</a>
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<a href="/react/contributing/how-to-contribute.html">How to Contribute</a>
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<a href="/react/contributing/codebase-overview.html">Codebase Overview</a>
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<a href="/react/contributing/implementation-notes.html">Implementation Notes</a>
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<a href="/react/contributing/design-principles.html">Design Principles</a>
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<a href="/react/docs/thinking-in-react.html">Thinking in React</a>
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<a href="/react/blog/">Blog</a>
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<a href="https://github.com/facebook/react" target="_blank">GitHub</a>
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<a href="http://facebook.github.io/react-native/" target="_blank">React Native</a>
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<a href="/react/acknowledgements.html">Acknowledgements</a>
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