Adding search capability to a static blog using the GitHub API

July 20, 2021

I just added a search feature to the home page, check it out!

Actually, it should even work here too.

This blog is fully static, written in Markdown, the source is hosted on GitHub, and the live site is hosted on some static site server. Depending on my current mood, it can be GitHub Pages, nginx, Netlify, Vercel, Render, or maybe CloudFlare or S3 in the future, who knows.

Regardless of the hosting service, because of the static nature of the blog, I can’t just run grep or similar on the server side to find matching pages and return results.

Since the blog source is hosted on GitHub as a public repository, the GitHub API was the obvious, most simple solution.

You can see the full source code here, but in this blog post, I’ll break it down for you.

The HTML part

I don’t use any framework on this blog, it’s vanilla everything.

For the search form, I just added this snippet.

<form class="search" onsubmit="return onSearchSubmit(this)">
  <p>Looking for something? Search the blog!</p>
  <p>
    <input type="text" name="query" placeholder="🔎">
    <button type="submit">Submit</button>
  </p>
  <div class="links posts"></div>
  <div class="message"></div>
</form>

By doing onsubmit="return onSearchSubmit(this)", I define the action inline from the markup. Passing this allows me to forward the current <form> element that’s being submitted for context, and the return allows to propagate a return false from the function to cancel the default behavior of submitting a query.

This is actually the oldest way of scripting events, and the browser support of this pattern is going to be way better than that of the async functions in my JS. 😂

This kind of code is often perceived as a bad practice, outdated, “smelly code”, “not clean” and so on by purists (including myself), because it usually results in poor maintainability, and it would be better to do something like:

document.querySelectorAll('form.search').forEach(form => {
  form.addEventListener('submit', onSearchSubmit)
})

On the other hand, this form is only going to be used on two pages on the blog (the home page and this very post), so I can afford the copy/paste maintenance tradeoff, and by tying the handler to the HTML, I don’t need my JS to look for form.search elements on every page load where most of the time there will be none. While this is as much of a performance issue as the inline event handler is a maintenance nightmare, I’ll favour this solution, just because.

Also, most modern front-end frameworks define event handlers in ways that are very close to the HTML onsubmit attribute, and I do like this way of doing things, so I’ll just apply that to vanilla HTML, even if that means using an “outdated” pattern.

That being said, for anything bigger than this use case, it’ll probably make more sense to use proper JS event handlers, or an actual framework. Consider yourself warned!

The JS part

Before going to the main JS code, I’ll introduce the helpers that it uses (don’t worry, there’s only two!).

The first one is called el and just adds some sugar around document.createElement, setting attributes and adding child nodes to it. I find it extremely convenient when scripting sites using vanilla JS.

function el (name, attrs = {}, children = []) {
  const element = document.createElement(name)

  for (const [key, value] of Object.entries(attrs)) {
    element[key] = value
  }

  for (const child of children) {
    element.appendChild(child)
  }

  return element
}

Then I have a more specific helper that empties both the results and message divs. This is useful because when show results, I also want to clear an eventual previous error message, and when showing an error, I want to clear an eventual previous results set.

function emptyFormData (form) {
  form.querySelector('.posts').textContent = ''
  form.querySelector('.message').textContent = ''
}

This is followed by another quick helper to set the message.

function formMessage (form, textContent) {
  emptyFormData(form)
  form.querySelector('.message').appendChild(el('p', { textContent }))
}

Now, to the interesting parts.

The submit part

The onSearchSubmit function needs to be defined globally to be callable from the HTML.

ESLint doesn’t like this, and thinks the function is unused (it can’t guess it’s being called from the HTML), so I need to add the comment above to ignore this warning.

// eslint-disable-next-line no-unused-vars
function onSearchSubmit (form) {
  searchBlog(form)
    .catch(err => {
      console.error(err)
      formMessage(form, 'An error occurred! Check the console. 🤭')
    })

  return false
}

It then calls the searchBlog asynchronous function, handles any error by logging it and showing a message using the formMessage helper.

Finally it returns false to prevent the default behavior of the form submission, which is to submit the form data as query parameters on the current URL.

The following is the breakdown of the searchBlog function, defined as:

async function searchBlog (form) {
  // Code goes here.
}

The search part

We start with a quick sanity check.

const query = form.query.value.trim().toLowerCase()

if (!query.length) {
  return
}

The GitHub repo for my blog is public, and the GitHub API can be called anonymously, without any kind of token, OAuth or other authentication mechanism.

This makes the search trivial to implement:

const q = `${query} in:file language:markdown repo:valeriangalliat/blog`

const result = await fetch(`https://api.github.com/search/code?q=${encodeURIComponent(q)}`)
  .then(res => res.json())

In practice, I also need to fetch the posts.html page which contains the links to all the posts on the blog. This will allow me to find the title of the pages that are matched without loading every single page. In the end the code looks like this:

const [result, posts] = await Promise.all([
  fetch(`https://api.github.com/search/code?q=${encodeURIComponent(q)}`)
    .then(res => res.json()),
  fetch('/posts.html')
    .then(res => res.text())
])

The render part

First, I remove index.md and posts.md from the results, since those pages include a lot of links to existing articles, they would be matched very often, and are not usually relevant.

const items = result.items.filter(item => !['index.md', 'posts.md'].includes(item.path))

Then, I add a quick check in case there was no match, again using the formMessage helper.

if (!items.length) {
  return formMessage(form, 'No matches found on the blog. 🥺')
}

Then I create a (native) DOMParser to parse the posts page, which allows me to querySelector the matched posts by href.

const parser = new DOMParser()
const postsDocument = parser.parseFromString(posts, 'text/html')

const lis = items.map(item => {
  const url = item.path.replace(/\.md$/, '.html')
  return postsDocument.querySelector(`a[href="${url}"]`).parentNode
})

In practice though, this page links posts relatively (e.g. 2021/07/post-title.md), while the search form could be included anywhere, and require an absolute link like /2021/07/post-title.md. To support this, we need to slightly modify the code:

const lis = items.map(item => {
  const relativeUrl = item.path.replace(/\.md$/, '.html')
  const url = `/${relativeUrl}`
  const a = postsDocument.querySelector(`a[href="${relativeUrl}"]`)

  a.href = url

  return a.parentNode
})

I also want to sort the results by most recent post. The date is included in a <small> element whose content is compatible with Date.parse so this is convenient:

lis.sort((a, b) => Date.parse(b.querySelector('small').textContent) - Date.parse(a.querySelecotr('small').textContent))

Finally I can show the results.

const ul = el('ul', {}, lis)

emptyFormData(form)
form.querySelector('.posts').appendChild(ul)

The reality is a bit more complex (just a bit)

This whole search feature is implemented in around 50 lines of code, HTML and JS combined, including helpers. And this is awesome.

In reality, I want to search not only blog posts, but also pages. Pages don’t have a date for me to sort with, and are not listed in posts.html so I can’t find their title instantly. Also some of my titles include a <small> element, so it’s something to take into account.

In the real code, I have to do a couple more things for this to work.

  1. Check if a matching <a> is found in the postsDocument, otherwise fetch the page itself and extract the <h1> as title.
  2. Take into account that pages don’t have a date when sorting, for example by using Date.parse(b.querySelector('small').textContent) || 0, so that we don’t try to subtract NaN which would mess up the sorting.

For the latter, I decided to add a customSortValue property to the li element instead, so that I can easily pass data from the loop to the sorting function. Not exactly clean, but so convenient.

This allows me to run Date.parse only once per result instead of running it at every iteration of the sort function, and removes the need to use the <small> element content for sorting, as it’s not always valid.

I also replaced li.querySelector('small') by li.lastElementChild to support posts that include a <small> element in the title.

Here’s the full code:

const lis = await Promise.all(items.map(async item => {
  const relativeUrl = item.path.replace(/\.md$/, '.html')
  const url = `/${relativeUrl}`
  const a = postsDocument.querySelector(`a[href="${relativeUrl}"]`)

  if (a) {
    const li = a.parentNode
    a.href = url
    const small = li.lastElementChild
    li.customSortValue = small ? Date.parse(small.textContent) : 0
    return li
  }

  // Fallback to fetching `<h1>` from actual page.
  const html = await fetch(url).then(res => res.text())
  const pageDocument = parser.parseFromString(html, 'text/html')

  return el('li', { customSortValue: 0 }, [
    el('a', {
      href: url,
      textContent: pageDocument.querySelector('h1').textContent
    }),
    el('small', {
      textContent: '—'
    })
  ])
}))

lis.sort((a, b) => b.customSortValue - a.customSortValue)

This block starts to be a bit long and could probably be refactored into different functions, but since it’s not code that I foresee evolving a lot, I’m fine with it like this.

Wrapping up

I hope you find this feature useful on the blog, or this code useful for you to implement a similar feature on your own site.

This tweet popped in my timeline yesterday, and couldn’t relate more. I think it illustrates perfectly the search implementation on this blog.

Code complexity

@flaviocopes, July 19, 2021

After more than 10 years building websites, I’ve had my fare share of frameworks, design patterns, bleeding edge libraries, compiling and transpiling everything possible and new cool, revolutionary ways of doing one thing or another.

While those kept me excited for many years, I ended up getting bored of it, and incidentally started writing boring code.

They’re all tools after all, and I won’t use them unless I have a good reason to.

Have a great day, and keep things simple! 🙏

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