mirror of
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synced 2025-11-01 09:12:30 +00:00
Paul O’Shannessy
609 lines
32 KiB
HTML
609 lines
32 KiB
HTML
<!DOCTYPE html>
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<!--[if IE]><![endif]-->
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<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>复合组件 | React</title>
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<meta name="viewport" content="width=device-width">
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<meta property="og:title" content="复合组件 | React">
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<meta property="og:type" content="website">
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<meta property="og:url" content="https://facebook.github.io/react/docs/multiple-components-zh-CN.html">
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<meta property="og:description" content="A JavaScript library for building user interfaces">
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<link rel="shortcut icon" href="/react/favicon.ico">
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<script src="/react/js/react.js"></script>
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<script src="/react/js/react-dom.js"></script>
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<script src="/react/js/live_editor.js"></script>
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</head>
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<body>
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<div class="container">
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<div class="nav-main">
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<div class="wrap">
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<a class="nav-home" href="/react/index.html">
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<img class="nav-logo" src="/react/img/logo.svg" width="36" height="36">
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React
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</a>
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<ul class="nav-site nav-site-internal">
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<li><a href="/react/docs/getting-started.html" class="active">Docs</a></li>
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<li><a href="/react/support.html">Support</a></li>
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<li><a href="/react/downloads.html">Download</a></li>
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<li><a href="/react/blog/">Blog</a></li>
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<li>
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<input id="algolia-doc-search" type="text" placeholder="Search docs..." />
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<ul class="nav-site nav-site-external">
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<li><a href="https://github.com/facebook/react">GitHub</a></li>
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<li><a href="https://facebook.github.io/react-native/">React Native</a></li>
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</ul>
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</div>
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</div>
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<section class="content wrap documentationContent">
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<div class="nav-docs">
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<!-- Docs Nav -->
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<div class="nav-docs-section">
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<h3>Quick Start</h3>
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<ul>
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<li>
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<a href="/react/docs/getting-started.html">Getting Started</a>
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</li>
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<li>
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<a href="/react/docs/tutorial.html">Tutorial</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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</li>
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</ul>
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</div>
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<div class="nav-docs-section">
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<h3>Community Resources</h3>
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<ul>
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<li>
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<a href="/react/docs/conferences.html">Conferences</a>
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</li>
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<li>
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<a href="/react/docs/videos.html">Videos</a>
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</li>
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<li>
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<a href="https://github.com/facebook/react/wiki/Complementary-Tools" class="external">Complementary Tools</a>
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</li>
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<li>
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<a href="https://github.com/facebook/react/wiki/Examples" class="external">Examples</a>
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</li>
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</ul>
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</div>
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<div class="nav-docs-section">
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<h3>Guides</h3>
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<ul>
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<li>
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<a href="/react/docs/why-react.html">Why React?</a>
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</li>
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<li>
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<a href="/react/docs/displaying-data.html">Displaying Data</a>
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<ul>
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<li>
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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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<li>
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<a href="/react/docs/jsx-spread.html">JSX Spread Attributes</a>
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</li>
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<li>
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<a href="/react/docs/jsx-gotchas.html">JSX Gotchas</a>
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</li>
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</ul>
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</li>
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<li>
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<a href="/react/docs/interactivity-and-dynamic-uis.html">Interactivity and Dynamic UIs</a>
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</li>
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<li>
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<a href="/react/docs/multiple-components.html">Multiple Components</a>
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</li>
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<li>
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<a href="/react/docs/reusable-components.html">Reusable Components</a>
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</li>
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<li>
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<a href="/react/docs/transferring-props.html">Transferring Props</a>
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</li>
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<li>
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<a href="/react/docs/forms.html">Forms</a>
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</li>
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<li>
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<a href="/react/docs/working-with-the-browser.html">Working With the Browser</a>
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<ul>
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<li>
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<a href="/react/docs/more-about-refs.html">Refs to Components</a>
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</li>
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</ul>
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</li>
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<li>
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<a href="/react/docs/tooling-integration.html">Tooling Integration</a>
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</li>
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<li>
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<a href="/react/docs/addons.html">Add-Ons</a>
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<ul>
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<li>
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<a href="/react/docs/animation.html">Animation</a>
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</li>
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<li>
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<a href="/react/docs/two-way-binding-helpers.html">Two-Way Binding Helpers</a>
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</li>
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<li>
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<a href="/react/docs/test-utils.html">Test Utilities</a>
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</li>
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<li>
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<a href="/react/docs/clone-with-props.html">Cloning Elements</a>
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</li>
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<li>
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<a href="/react/docs/create-fragment.html">Keyed Fragments</a>
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</li>
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<li>
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<a href="/react/docs/update.html">Immutability Helpers</a>
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</li>
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<li>
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<a href="/react/docs/pure-render-mixin.html">PureRenderMixin</a>
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</li>
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<li>
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<a href="/react/docs/perf.html">Performance Tools</a>
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</li>
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<li>
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<a href="/react/docs/shallow-compare.html">Shallow Compare</a>
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</li>
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</ul>
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</li>
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<li>
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<a href="/react/docs/advanced-performance.html">Advanced Performance</a>
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</li>
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<li>
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<a href="/react/docs/context.html">Context</a>
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</li>
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</ul>
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</div>
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<div class="nav-docs-section">
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<h3>Reference</h3>
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<ul>
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<li>
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<a href="/react/docs/top-level-api.html">Top-Level API</a>
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</li>
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<li>
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<a href="/react/docs/component-api.html">Component API</a>
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</li>
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<li>
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<a href="/react/docs/component-specs.html">Component Specs and Lifecycle</a>
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</li>
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<li>
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<a href="/react/docs/tags-and-attributes.html">Supported Tags and Attributes</a>
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</li>
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<li>
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<a href="/react/docs/events.html">Event System</a>
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</li>
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<li>
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<a href="/react/docs/dom-differences.html">DOM Differences</a>
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</li>
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<li>
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<a href="/react/docs/special-non-dom-attributes.html">Special Non-DOM Attributes</a>
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</li>
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<li>
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<a href="/react/docs/reconciliation.html">Reconciliation</a>
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</li>
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<li>
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<a href="/react/docs/webcomponents.html">Web Components</a>
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</li>
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<li>
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<a href="/react/docs/glossary.html">React (Virtual) DOM Terminology</a>
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</li>
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</ul>
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</div>
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<div class="nav-docs-section">
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<h3>Flux</h3>
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<ul>
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<li>
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<a href="https://facebook.github.io/flux/docs/overview.html" class="external">Flux Overview</a>
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</li>
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<li>
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<a href="https://facebook.github.io/flux/docs/todo-list.html" class="external">Flux TodoMVC Tutorial</a>
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</li>
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</ul>
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</div>
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<!-- Tips Nav -->
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<div class="nav-docs-section">
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<h3>Tips</h3>
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<ul>
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<li>
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<a href="/react/tips/introduction.html">Introduction</a>
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</li>
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<li>
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<a href="/react/tips/inline-styles.html">Inline Styles</a>
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</li>
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<li>
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<a href="/react/tips/if-else-in-JSX.html">If-Else in JSX</a>
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</li>
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<li>
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<a href="/react/tips/self-closing-tag.html">Self-Closing Tag</a>
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</li>
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<li>
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<a href="/react/tips/maximum-number-of-jsx-root-nodes.html">Maximum Number of JSX Root Nodes</a>
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</li>
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<li>
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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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</li>
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<li>
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<a href="/react/tips/children-props-type.html">Type of the Children props</a>
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</li>
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<li>
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<a href="/react/tips/controlled-input-null-value.html">Value of null for Controlled Input</a>
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</li>
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<li>
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<a href="/react/tips/componentWillReceiveProps-not-triggered-after-mounting.html">componentWillReceiveProps Not Triggered After Mounting</a>
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</li>
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<li>
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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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</li>
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<li>
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<a href="/react/tips/dom-event-listeners.html">DOM Event Listeners in a Component</a>
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</li>
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<li>
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<a href="/react/tips/initial-ajax.html">Load Initial Data via AJAX</a>
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</li>
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<li>
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<a href="/react/tips/false-in-jsx.html">False in JSX</a>
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</li>
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<li>
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<a href="/react/tips/communicate-between-components.html">Communicate Between Components</a>
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</li>
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<li>
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<a href="/react/tips/expose-component-functions.html">Expose Component Functions</a>
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</li>
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<li>
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<a href="/react/tips/children-undefined.html">this.props.children undefined</a>
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</li>
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<li>
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<a href="/react/tips/use-react-with-other-libraries.html">Use React with Other Libraries</a>
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</li>
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<li>
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<a href="/react/tips/dangerously-set-inner-html.html">Dangerously Set innerHTML</a>
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</li>
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</ul>
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</div>
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</div>
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<div class="inner-content">
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<h1>
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复合组件
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<a class="edit-page-link" href="https://github.com/facebook/react/tree/master/docs/docs/04-multiple-components.zh-CN.md" target="_blank">Edit on GitHub</a>
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</h1>
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<div class="subHeader"></div>
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<p>目前为止，我们已经学了如何用单个组件来展示数据和处理用户输入。下一步让我们来体验 React 最激动人心的特性之一：可组合性（composability）。</p>
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<h2><a class="anchor" name=""></a>动机：关注分离 <a class="hash-link" href="#">#</a></h2>
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<p>通过复用那些接口定义良好的组件来开发新的模块化组件，我们得到了与使用函数和类相似的好处。具体来说就是能够通过开发简单的组件把程序的<em>不同关注面分离</em>。如果为程序开发一套自定义的组件库，那么就能以最适合业务场景的方式来展示你的用户界面。</p>
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<h2><a class="anchor" name=""></a>组合实例 <a class="hash-link" href="#">#</a></h2>
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<p>让我们用 Facebook Graph API 来开发一个显示 Facebook 页面图片和用户名的简单 Avatar 组件吧。</p>
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<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="kd">var</span> <span class="nx">Avatar</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span>
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<span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
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<span class="k">return</span> <span class="p">(</span>
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<span class="o"><</span><span class="nx">div</span><span class="o">></span>
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<span class="o"><</span><span class="nx">PagePic</span> <span class="nx">pagename</span><span class="o">=</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">pagename</span><span class="p">}</span> <span class="o">/></span>
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<span class="o"><</span><span class="nx">PageLink</span> <span class="nx">pagename</span><span class="o">=</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">pagename</span><span class="p">}</span> <span class="o">/></span>
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<span class="o"><</span><span class="err">/div></span>
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<span class="p">);</span>
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<span class="p">}</span>
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<span class="p">});</span>
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<span class="kd">var</span> <span class="nx">PagePic</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span>
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<span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
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<span class="k">return</span> <span class="p">(</span>
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<span class="o"><</span><span class="nx">img</span> <span class="nx">src</span><span class="o">=</span><span class="p">{</span><span class="s1">'https://graph.facebook.com/'</span> <span class="o">+</span> <span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">pagename</span> <span class="o">+</span> <span class="s1">'/picture'</span><span class="p">}</span> <span class="o">/></span>
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<span class="p">);</span>
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<span class="p">}</span>
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<span class="p">});</span>
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<span class="kd">var</span> <span class="nx">PageLink</span> <span class="o">=</span> <span class="nx">React</span><span class="p">.</span><span class="nx">createClass</span><span class="p">({</span>
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<span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
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<span class="k">return</span> <span class="p">(</span>
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<span class="o"><</span><span class="nx">a</span> <span class="nx">href</span><span class="o">=</span><span class="p">{</span><span class="s1">'https://www.facebook.com/'</span> <span class="o">+</span> <span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">pagename</span><span class="p">}</span><span class="o">></span>
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<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">pagename</span><span class="p">}</span>
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<span class="o"><</span><span class="err">/a></span>
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<span class="p">);</span>
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<span class="p">}</span>
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<span class="p">});</span>
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<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">Avatar</span> <span class="nx">pagename</span><span class="o">=</span><span class="s2">"Engineering"</span> <span class="o">/></span><span class="p">,</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">'example'</span><span class="p">)</span>
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<span class="p">);</span>
|
||
</code></pre></div><h2><a class="anchor" name=""></a>从属关系 <a class="hash-link" href="#">#</a></h2>
|
||
<p>上面例子中，<code>Avatar</code> 拥有 <code>PagePic</code> 和 <code>PageLink</code> 的实例。<code>拥有者</code> 就是给其它组件设置 <code>props</code> 的那个组件。更正式地说，如果组件 <code>Y</code> 在 <code>render()</code> 方法是创建了组件 <code>X</code>，那么 <code>Y</code> 就拥有 <code>X</code>。上面讲过，组件不能修改自身的 <code>props</code> - 它们总是与它们拥有者设置的保持一致。这是保持用户界面一致性的基本不变量。</p>
|
||
|
||
<p>把从属关系与父子关系加以区别至关重要。从属关系是 React 特有的，而父子关系简单来讲就是DOM 里的标签的关系。在上一个例子中，<code>Avatar</code> 拥有 <code>div</code>、<code>PagePic</code> 和 <code>PageLink</code> 实例，<code>div</code> 是 <code>PagePic</code> 和 <code>PageLink</code> 实例的<strong>父级</strong>（但不是拥有者）。</p>
|
||
<h2><a class="anchor" name=""></a>子级 <a class="hash-link" href="#">#</a></h2>
|
||
<p>实例化 React 组件时，你可以在开始标签和结束标签之间引用在React 组件或者Javascript 表达式：</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="o"><</span><span class="nx">Parent</span><span class="o">><</span><span class="nx">Child</span> <span class="o">/><</span><span class="err">/Parent></span>
|
||
</code></pre></div>
|
||
<p><code>Parent</code> 能通过专门的 <code>this.props.children</code> props 读取子级。<strong><code>this.props.children</code> 是一个不透明的数据结构：</strong> 通过 <a href="/react/docs/top-level-api.html#react.children">React.Children 工具类</a> 来操作。</p>
|
||
<h3><a class="anchor" name="reconciliation"></a>子级校正（Reconciliation） <a class="hash-link" href="#reconciliation">#</a></h3>
|
||
<p><strong>校正就是每次 render 方法调用后 React 更新 DOM 的过程。</strong> 一般情况下，子级会根据它们被渲染的顺序来做校正。例如，下面代码描述了两次渲染的过程：</p>
|
||
<div class="highlight"><pre><code class="language-html" data-lang="html">// 第一次渲染
|
||
<span class="nt"><Card></span>
|
||
<span class="nt"><p></span>Paragraph 1<span class="nt"></p></span>
|
||
<span class="nt"><p></span>Paragraph 2<span class="nt"></p></span>
|
||
<span class="nt"></Card></span>
|
||
// 第二次渲染
|
||
<span class="nt"><Card></span>
|
||
<span class="nt"><p></span>Paragraph 2<span class="nt"></p></span>
|
||
<span class="nt"></Card></span>
|
||
</code></pre></div>
|
||
<p>直观来看，只是删除了<code><p>Paragraph 1</p></code>。事实上，React 先更新第一个子级的内容，然后删除最后一个组件。React 是根据子级的<em>顺序</em>来校正的。</p>
|
||
<h3><a class="anchor" name=""></a>子组件状态管理 <a class="hash-link" href="#">#</a></h3>
|
||
<p>对于大多数组件，这没什么大碍。但是，对于使用 <code>this.state</code> 来在多次渲染过程中里维持数据的状态化组件，这样做潜在很多问题。</p>
|
||
|
||
<p>多数情况下，可以通过隐藏组件而不是删除它们来绕过这些问题。</p>
|
||
<div class="highlight"><pre><code class="language-html" data-lang="html">// 第一次渲染
|
||
<span class="nt"><Card></span>
|
||
<span class="nt"><p></span>Paragraph 1<span class="nt"></p></span>
|
||
<span class="nt"><p></span>Paragraph 2<span class="nt"></p></span>
|
||
<span class="nt"></Card></span>
|
||
// 第二次渲染
|
||
<span class="nt"><Card></span>
|
||
<span class="nt"><p</span> <span class="na">style=</span><span class="s">{{display:</span> <span class="err">'</span><span class="na">none</span><span class="err">'}}</span><span class="nt">></span>Paragraph 1<span class="nt"></p></span>
|
||
<span class="nt"><p></span>Paragraph 2<span class="nt"></p></span>
|
||
<span class="nt"></Card></span>
|
||
</code></pre></div><h3><a class="anchor" name=""></a>动态子级 <a class="hash-link" href="#">#</a></h3>
|
||
<p>如果子组件位置会改变（如在搜索结果中）或者有新组件添加到列表开头（如在流中）情况会变得更加复杂。如果子级要在多个渲染阶段保持自己的特征和状态，在这种情况下，你可以通过给子级设置惟一标识的 <code>key</code> 来区分。</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"> <span class="nx">render</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
|
||
<span class="kd">var</span> <span class="nx">results</span> <span class="o">=</span> <span class="k">this</span><span class="p">.</span><span class="nx">props</span><span class="p">.</span><span class="nx">results</span><span class="p">;</span>
|
||
<span class="k">return</span> <span class="p">(</span>
|
||
<span class="o"><</span><span class="nx">ol</span><span class="o">></span>
|
||
<span class="p">{</span><span class="nx">results</span><span class="p">.</span><span class="nx">map</span><span class="p">(</span><span class="kd">function</span><span class="p">(</span><span class="nx">result</span><span class="p">)</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="o"><</span><span class="nx">li</span> <span class="nx">key</span><span class="o">=</span><span class="p">{</span><span class="nx">result</span><span class="p">.</span><span class="nx">id</span><span class="p">}</span><span class="o">></span><span class="p">{</span><span class="nx">result</span><span class="p">.</span><span class="nx">text</span><span class="p">}</span><span class="o"><</span><span class="err">/li>;</span>
|
||
<span class="p">})}</span>
|
||
<span class="o"><</span><span class="err">/ol></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
</code></pre></div>
|
||
<p>当 React 校正带有 key 的子级时，它会确保它们被重新排序（而不是破坏）或者删除（而不是重用）。
|
||
<code>务必</code> 把 <code>key</code> 添加到子级数组里组件本身上，而不是每个子级内部最外层 HTML 上：</p>
|
||
<div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="c1">// 错误！</span>
|
||
<span class="kd">var</span> <span class="nx">ListItemWrapper</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="o"><</span><span class="nx">li</span> <span class="nx">key</span><span class="o">=</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">data</span><span class="p">.</span><span class="nx">id</span><span class="p">}</span><span class="o">></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">data</span><span class="p">.</span><span class="nx">text</span><span class="p">}</span><span class="o"><</span><span class="err">/li>;</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
<span class="kd">var</span> <span class="nx">MyComponent</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"><</span><span class="nx">ul</span><span class="o">></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">results</span><span class="p">.</span><span class="nx">map</span><span class="p">(</span><span class="kd">function</span><span class="p">(</span><span class="nx">result</span><span class="p">)</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="o"><</span><span class="nx">ListItemWrapper</span> <span class="nx">data</span><span class="o">=</span><span class="p">{</span><span class="nx">result</span><span class="p">}</span><span class="o">/></span><span class="p">;</span>
|
||
<span class="p">})}</span>
|
||
<span class="o"><</span><span class="err">/ul></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
</code></pre></div><div class="highlight"><pre><code class="language-javascript" data-lang="javascript"><span class="c1">// 正确 :)</span>
|
||
<span class="kd">var</span> <span class="nx">ListItemWrapper</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="o"><</span><span class="nx">li</span><span class="o">></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">data</span><span class="p">.</span><span class="nx">text</span><span class="p">}</span><span class="o"><</span><span class="err">/li>;</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
<span class="kd">var</span> <span class="nx">MyComponent</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"><</span><span class="nx">ul</span><span class="o">></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">results</span><span class="p">.</span><span class="nx">map</span><span class="p">(</span><span class="kd">function</span><span class="p">(</span><span class="nx">result</span><span class="p">)</span> <span class="p">{</span>
|
||
<span class="k">return</span> <span class="o"><</span><span class="nx">ListItemWrapper</span> <span class="nx">key</span><span class="o">=</span><span class="p">{</span><span class="nx">result</span><span class="p">.</span><span class="nx">id</span><span class="p">}</span> <span class="nx">data</span><span class="o">=</span><span class="p">{</span><span class="nx">result</span><span class="p">}</span><span class="o">/></span><span class="p">;</span>
|
||
<span class="p">})}</span>
|
||
<span class="o"><</span><span class="err">/ul></span>
|
||
<span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="p">});</span>
|
||
</code></pre></div>
|
||
<p>也可以传递ReactFragment 对象 来做有 key 的子级。详见<a href="create-fragment.html">Keyed Fragments</a></p>
|
||
<h2><a class="anchor" name=""></a>数据流 <a class="hash-link" href="#">#</a></h2>
|
||
<p>React 里，数据通过上面介绍过的 <code>props</code> 从拥有者流向归属者。这就是高效的单向数据绑定(one-way data binding)：拥有者通过它的 <code>props</code> 或 <code>state</code> 计算出一些值，并把这些值绑定到它们拥有的组件的 props 上。因为这个过程会递归地调用，所以数据变化会自动在所有被使用的地方自动反映出来。</p>
|
||
<h2><a class="anchor" name=""></a>性能提醒 <a class="hash-link" href="#">#</a></h2>
|
||
<p>你或许会担心如果一个拥有者有大量子级时，对于数据变化做出响应非常耗费性能。值得庆幸的是执行 JavaScript 非常的快，而且 <code>render()</code> 方法一般比较简单，所以在大部分应用里这样做速度极快。此外，性能的瓶颈大多是因为 DOM 更新，而非 JS 执行，而且 React 会通过批量更新和变化检测来优化性能。</p>
|
||
|
||
<p>但是，有时候需要做细粒度的性能控制。这种情况下，可以重写 <code>shouldComponentUpdate()</code> 方法返回 false 来让 React 跳过对子树的处理。参考 <a href="/react/docs/component-specs.html">React reference docs</a> 了解更多。</p>
|
||
|
||
<blockquote>
|
||
<p>注意：</p>
|
||
|
||
<p>如果在数据变化时让 <code>shouldComponentUpdate()</code> 返回 false，React 就不能保证用户界面同步。当使用它的时候一定确保你清楚到底做了什么，并且只在遇到明显性能问题的时候才使用它。不要低估 JavaScript 的速度，DOM 操作通常才是慢的原因。</p>
|
||
</blockquote>
|
||
|
||
|
||
<div class="docs-prevnext">
|
||
|
||
<a class="docs-prev" href="/react/docs/interactivity-and-dynamic-uis-zh-CN.html">← Prev</a>
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|
||
<a class="docs-next" href="/react/docs/reusable-components-zh-CN.html">Next →</a>
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||
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|
||
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|
||
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|
||
|
||
|
||
<footer class="wrap">
|
||
<div class="left">
|
||
A Facebook & Instagram collaboration.<br>
|
||
<a href="/react/acknowledgements.html">Acknowledgements</a>
|
||
</div>
|
||
<div class="right">
|
||
© 2013–2016 Facebook Inc.<br>
|
||
Documentation licensed under <a href="https://creativecommons.org/licenses/by/4.0/">CC BY 4.0</a>.
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