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Add reading time

Create a remark plugin which adds a reading time property to the frontmatter of your Markdown or MDX files. Use this property to display the reading time for each page.

Recipe

Section titled Recipe

  1. Install Helper Packages

    Install these two helper packages:

    Terminal window
    npm install reading-time mdast-util-to-string

  2. Create a remark plugin.

    This plugin uses the mdast-util-to-string package to get the Markdown file’s text. This text is then passed to the reading-time package to calculate the reading time in minutes.

    remark-reading-time.mjs
    import getReadingTime from 'reading-time';
    import { toString } from 'mdast-util-to-string';
    

    export function remarkReadingTime() {
      return function (tree, { data }) {
        const textOnPage = toString(tree);
        const readingTime = getReadingTime(textOnPage);
        // readingTime.text will give us minutes read as a friendly string,
        // i.e. "3 min read"
        data.astro.frontmatter.minutesRead = readingTime.text;
      };
    }

  3. Add the plugin to your config:

    astro.config.mjs
    import { defineConfig } from 'astro/config';
    import { remarkReadingTime } from './remark-reading-time.mjs';
    

    export default defineConfig({
      markdown: {
        remarkPlugins: [remarkReadingTime],
      },
    });

    Now all Markdown documents will have a calculated minutesRead property in their frontmatter.

  4. Display Reading Time

    If your blog posts are stored in a content collection, access the remarkPluginFrontmatter from the render(entry) function. Then, render minutesRead in your template wherever you would like it to appear.

    src/pages/posts/[slug].astro
    ---
    import { getCollection, render } from 'astro:content';
    

    export async function getStaticPaths() {
      const blog = await getCollection('blog');
      return blog.map(entry => ({
        params: { slug: entry.id },
        props: { entry },
      }));
    }
    

    const { entry } = Astro.props;
    const { Content, remarkPluginFrontmatter } = await render(entry);
    ---
    

    <html>
      <head>...</head>
      <body>
        ...
        <p>{remarkPluginFrontmatter.minutesRead}</p>
        ...
      </body>
    </html>

    If you’re using a Markdown layout, use the minutesRead frontmatter property from Astro.props in your layout template.

    src/layouts/BlogLayout.astro
    ---
    const { minutesRead } = Astro.props.frontmatter;
    ---
    

    <html>
      <head>...</head>
      <body>
        <p>{minutesRead}</p>
        <slot />
      </body>
    </html>
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