Building with Components

To use Gatsby, you will need a basic understanding of React components.

The official tutorial is a good place to start.

Why React components?

React’s component architecture simplifies building large websites by encouraging modularity, reusability, and clear abstractions. React has a large ecosystem of open source components, tutorials, and tooling that can be used seamlessly for building sites with Gatsby. Gatsby is built to behave almost exactly like a normal React application.

Thinking in React is a good resource for learning how to structure applications with React.

How does Gatsby use React Components?

Everything in Gatsby is built using components.

A basic directory structure of a project might look like this:

.
├── gatsby-config.js
├── package.json
└── src
    ├── html.jsx
    ├── pages
    │   ├── index.jsx
    │   └── posts
    │       ├── 01-01-2017
    │       │   └── index.md
    │       ├── 01-02-2017
    │       │   └── index.md
    │       └── 01-03-2017
    │           └── index.md
    ├── templates
        └── post.jsx

Page components

Components under src/pages become pages automatically with paths based on their file name. For example src/pages/index.jsx is mapped to yoursite.com and src/pages/about.jsx becomes yoursite.com/about/. Every .js or .jsx file in the pages directory must resolve to either a string or react component, otherwise your build will fail.

Example:

src/pages/about.jsx

import React from "react"

function AboutPage(props) {
  return (
    <div className="about-container">
      <p>About me.</p>
    </div>
  )
}

export default AboutPage

Page template components

You can programmatically create pages using “page template components”. All pages are React components but very often these components are just wrappers around data from files or other sources.

src/templates/post.jsx is an example of a page component. It queries GraphQL for markdown data and then renders the page using this data.

See part seven of the tutorial for a detailed introduction to programmatically creating pages.

Example:

src/templates/post.jsx

import React from "react"
import { graphql } from "gatsby"

function BlogPostTemplate(props) {
  const post = props.data.markdownRemark
  return (
    <div>
      <h1>{post.frontmatter.title}</h1>
      <div dangerouslySetInnerHTML={{ __html: post.html }} />
    </div>
  )
}

export default BlogPostTemplate

export const pageQuery = graphql`
  query($slug: String!) {
    markdownRemark(fields: { slug: { eq: $slug } }) {
      html
      frontmatter {
        title
      }
    }
  }
`

HTML component

src/html.jsx is responsible for everything other than where Gatsby lives in the <body />.

In this file, you can modify the <head> metadata and general structure of the document and add external links.

Typically you should omit this from your site as the default html.js file will suffice. If you need more control over server rendering, then it’s valuable to have an html.js.

Example:

src/html.jsx

import React from "react"
import favicon from "./favicon.png"

let inlinedStyles = ""
if (process.env.NODE_ENV === "production") {
  try {
    inlinedStyles = require("!raw-loader!../public/styles.css")
  } catch (e) {
    console.log(e)
  }
}

function HTML(props) {
  let css
  if (process.env.NODE_ENV === "production") {
    css = (
      <style
        id="gatsby-inlined-css"
        dangerouslySetInnerHTML={{ __html: inlinedStyles }}
      />
    )
  }
  return (
    <html lang="en">
      <head>
        <meta charSet="utf-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        {props.headComponents}
        <link rel="shortcut icon" href={favicon} />
        {css}
      </head>
      <body>
        <div id="___gatsby" dangerouslySetInnerHTML={{ __html: props.body }} />
        {props.postBodyComponents}
      </body>
    </html>
  )
}

These are examples of the different ways React components are used in Gatsby sites. To see full working examples, check out the examples directory in the Gatsby repo.

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