React apps are made out of ''components''. A component is a piece of the UI (user interface) that has its own logic and appearance. A component can be as small as a button, or as large as an entire page.
# GET STARTED
#* [[React - Quick Start|Quick Start]]
# LEARN REACT
React components are JavaScript functions that return markup:
== 備忘メモ ==
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Now that you’ve declared <code>MyButton</code>, you can nest it into another component:
Notice that <code><MyButton /></code> starts with a capital letter. That’s how you know it’s a React component. React component names must always start with a capital letter, while HTML tags must be lowercase.