How can I render a astro component to a HTML string?

Question

I'd like to be able to have a dynamic page in Astro that renders out an Astro component. I've dug into the docs and code, and couldn't find a function like the one below (Astro.render). Ideally, I can pass properties into it. I'm looking for something similar to react.renderToString.

import Example from './components/Example.astro'

export async function get() {
  return {
    body: Astro.render(Example)
  };
}

Update: I think every answer here is getting this wrong. Given an astro file, I want a function within the node runtime astro framework independent that can take an astro file and simply return a Response (because I know astro files can return a response from front-matter) and or HTML string? I'd think it can be a tuple like [res, htmlString]. Just like a markdown file can be converted, an astro file as well should be able to be processed.

Answer 1

Render Astro Component to html string using Slots

rendering to a html string do exist in Astro, but for slots, if you pass your component in another Wrapper/Serialiser, you can get its html string easily

Working example

• github repo https://github.com/MicroWebStacks/astro-examples#16_html-string

• CodeSandbox https://stackblitz.com/github/MicroWebStacks/astro-examples/tree/main/16_html-string

Usage

This is the body of the Wrapper component, it is being used such as for highlighting but also rendered with the Fragment component

---
const html = await Astro.slots.render('default');
import { Code } from 'astro/components';
---
<Fragment set:html={html} />

<Code code={html} lang="html" />

The usage is as follows

in e.g. index.astro

---
import Card from '../components/Card.astro';
import StringWrapper from '../components/StringWrapper.astro';
...
---
    <StringWrapper>
        <Card title="Test" />
    </StringWrapper>

Answer 2

@HappyDev's suggestion inspired this – while not particularly abstracted and could need some refactoring it does work and allows you to build Astro pages in Strapi using its dynamic zones and components by building corresponding Astro components:

/pages/index.astro

import SectionType1 from '../components/sections/SectionType1.astro'
// Import all the components you use to ensure styles and scripts are injected`
import renderPageContent from '../helpers/renderPageContent'
const page = await fetch(STRAPIENDPOINT) // <-- Strapi JSON
const contentParts = page.data.attributes.Sections 
const pageContentString = await renderPageContent(contentParts)
---
<Layout>
    <div set:html={pageContentString}></div>
</Layout>   

/helpers/renderPageContent.js

export default async function (parts) {

  const pagePartsContent = [];
  parts.forEach(function (part) {
    let componentRequest = {};

    switch (part.__component) {

      case "sections.SectionType1":
        componentRequest.path = "SectionType1";
        componentRequest.params = {
          title: part.Title, // Your Strapi fields for this component
          text: part.Text    // watch out for capitalization
        };
        break;

// Add more cases for each component type and its fields

    }
    if (Object.keys(componentRequest).length) {
      pagePartsContent.push(componentRequest);
    }
  });

  let pagePartsContentString = "";
  
  for (const componentRequest of pagePartsContent) {
    let response = await fetch(
      `${import.meta.env.SITE_URL}/components/${
        componentRequest.path
      }?data=${encodeURIComponent(JSON.stringify(componentRequest.params))}`
    );

    let contentString = await response.text();
    // Strip out everything but the component markup so we avoid getting style and script tags in the body
    contentString = contentString.match(/(<section.*?>.*<\/section>)/gims)[0];
    pagePartsContentString += contentString;
  }

  return pagePartsContentString;
}

/components/sections/SectionType1.astro

---
export interface Props {
  title: string;
  text?: string;
}

const { title, text } = Astro.props as Props;
---
<section>
  <h1>{ title }</h1>
  <p>{ text }</p>
</section>

/pages/components/SectionType1.astro

---
import SectionType1 from '../../components/sections/SectionType1.astro';
import urlParser from '../../helpers/urlparser'
const { title, text } = urlParser(Astro.url);
---
<SectionType1
  title={title}
  text={text}
  />

/helpers/urlParser.js

export default function(url) {
  return JSON.parse(Object.fromEntries(new URL(url).searchParams).data)
}