Mapping JS components to (Gutenberg) blocks

This guide presents an example Preact app that queries for block data and maps it into customized JavaScript components.

⚙️ Configuration alert:

In order to run the Preact app below as a static .html file in the browser, the Schema Configuration applied to the endpoint needs to have Response Headers with the following value:

Access-Control-Allow-Origin: null
Access-Control-Allow-Headers: content-type,content-length,accept

(The HTML code below is inspired by the Preact example in Automattic/vip-block-data-api.)

The GraphQL query contained in the code below retrieves the post's block data as a JSON object (via field CustomPost.blockDataItems), and then the JavaScript code maps each block data item into a custom component:

<!DOCTYPE html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Gato GraphQL - Mapping JS components to (Gutenberg) blocks: Preact example</title>
</head>

<body></body>

<script type="module">
import { h, render } from 'https://esm.sh/preact';

// Input here your domain, and enable the single endpoint
const endpoint = "https://mysite.com/graphql/";

// Input here the ID of a post with blocks
const postId = 40;

renderPost(endpoint, postId);

async function renderPost(endpoint, postId) {
const data = {
query: `
query GetPost($postId: ID!) {
post(by: { id: $postId }) {
title
blockDataItems
}
}
`
,
variables: {
postId: `${ postId }`
},
};

const response = await fetch(
endpoint,
{
method: 'post',
body: JSON.stringify(data),
headers: {
Accept: 'application/json',
'Content-Type': 'application/json',
'Content-Length': data.length,
},
}
);

// Execute the query, and await the response
const json = await response.json();

// If the query produced errors, exit
if (json.errors) {
console.log(JSON.stringify(json.errors));
return;
}

// Uncomment here to visualize the GraphQL response
// console.log(json.data);

const postTitle = json.data.post?.title;
const blocks = json.data.post?.blockDataItems;

const App = Post(postTitle, blocks);
render(App, document.body);
}

function mapBlockToComponent(block) {
if (block.name === 'core/heading') {
return Heading(block);
} else if (block.name === 'core/paragraph') {
return Paragraph(block);
} else if (block.name === 'core/media-text') {
return MediaText(block);
} else if (block.name === 'core/gallery') {
return Gallery(block);
} else if (block.name === 'core/image') {
return Image(block);
} else {
return null;
}
}

/* Components */

function Post(title, blocks) {
return h('div', { className: 'post' },
h('h1', null, title),
blocks.map(mapBlockToComponent),
);
}

function Heading(props) {
// Use dangerouslySetInnerHTML for rich text formatting
return h('h2', { dangerouslySetInnerHTML: { __html: props.attributes.content } });
}

function Paragraph(props) {
// Use dangerouslySetInnerHTML for rich text formatting
return h('p', { dangerouslySetInnerHTML: { __html: props.attributes.content } });
}

function MediaText(props) {
return h('div', { className: 'media-text' },
h('div', { className: 'media' },
h('img', { src: props.attributes.mediaUrl })
),
h('div', { className: 'text' },
props.innerBlocks ? props.innerBlocks.map(mapBlockToComponent) : null,
),
)
}

function Gallery(props) {
return h('div', { className: 'gallery' },
h('div', { className: 'images' },
props.innerBlocks ? props.innerBlocks.map(mapBlockToComponent) : null,
),
)
}

function Image(props) {
return h('img', { src: props.attributes.url });
}
</script>
</html>

Running the application produces the following HTML code from post data:

<div class="post">
<h1>Welcome to a single post full of blocks!</h1>
<p>When I look back on my past and think how much time I wasted on nothing, how much time has been lost in futilities, errors, laziness, incapacity to live; how little I appreciated it, how many times I sinned against my heart and soul-then my heart bleeds. <strong>Life is a gift, life is happiness, every minute can be an eternity of happiness</strong>. (<a href="https://www.azquotes.com/author/4085-Fyodor_Dostoevsky" target="_blank" rel="noopener">Quote by Fyodor Dostoevsky</a>)<br></p>
<h2>This blog post will be transformed...</h2>
<p>If you make it a habit not to blame others, you will feel the growth of the ability to love in your soul, and you will see the growth of goodness in your life. (<a href="https://www.azquotes.com/author/14706-Leo_Tolstoy" target="_blank" rel="noopener">Quote by Leo Tolstoy</a>)<br></p>
<img src="https://i.ytimg.com/vi/z4KKd2nGlEM/maxresdefault.jpg">
<h2><mark style="background-color:#D1D1E4" class="has-inline-color">I love these veggies!!!</mark></h2>
<h2>When going to eat out, I normally go for one of these:</h2>
<h2>This heading (H3) is boring (Regex test: $1 #1), but these guys are not</h2>
<div class="gallery">
<div class="images">
<img src="https://i.insider.com/5f44388342f43f001ddfec52">
<img src="https://i.pinimg.com/originals/85/a7/f5/85a7f5cee4c93cb3995d1b51e3a0289f.jpg">
</div>
</div>
</div>