Add search with Lunr

lunr.js is a neat little Javascript library that allows to equip your website with a search functionality fairly easily.

The steps below show a simple way of doing this matching what is done on this website. Once it's working, you might want to adjust the build_index.js and/or the lunrclient.js to match your needs.

Pre-requisites

Libraries

Install lunr and cheerio (a HTML parser) with node:

$> npm install lunr
$> npm install cheerio

(you might have to add sudo before npm).

Files

Copy this folder to a /_libs/lunr/ directory. Discard the lunr_index.js which is the index of this website, you will rebuild your own of course!

The important files are build_index.js and lunrclient.js (of which a minified version is provided which you will want to re-generate if you modify the base file). These files are adapted from this repository which shows how to use Lunr on a static website.

You can choose whether to serve your own copy of lunr.min.js (done here) or to use an online version via

<script src="https://unpkg.com/lunr/lunr.js"></script>

Index builder

The file build_index.js does the following:

  • it goes over all files in a HTML_FOLDER (by default: /__site/),

  • it builds an index lunr_index.js which can subsequently be queried upon the user entering search terms.

By default, the index built is fairly barebone to reduce the size of the generated index. If you want fancier search, you might want to modify this a bit to add a preview of the page, boost results depending on where there are (title, keyword, ...), add stop words, etc. (Refer to the Lunr docs for this as well as the example repo mentioned earlier or Documenter.jl's version).

⚠ Note
Modify this file at will but be careful with the lines with PATH_PREPEND if your website is a project website (i.e. the root URL is something like username.github.io/project/). These lines help ensure that the generated links are valid. See also the section on updating the index.

Client

The file lunrclient.js (and its minified version) does the following:

  • query the index

  • display the results

You might want to modify the parseLunrResults if you want the results to be displayed differently.

⚠ Note
If you modify this file, make sure it's called properly in the src/_html_parts/index.html and, eventually, minify it.

Adding a form in head.html

The search box on this website is added with the following HTML in _layout/head.html:

<!doctype html>
<!-- first few lines ... -->
  <script src="/libs/lunr/lunr.min.js"></script>
  <script src="/libs/lunr/lunr_index.js"></script>
  <script src="/libs/lunr/lunrclient.min.js"></script>
</head>
<!-- ... -->
<form id="lunrSearchForm" name="lunrSearchForm">
  <input class="search-input" name="q" placeholder="Enter search term" type="text">
  <input type="submit" value="Search" formaction="/search/index.html">
</form>
<-- ... -->

You may want to style it a bit like so:

.result-title a { text-decoration: none; }
.result-title a:hover { text-decoration: underline; }
.result-preview { color: #808080; }
.resultCount { color: #808080; }
.result-query { font-weight: bold; }
#lunrSearchForm { margin-top: 1em; }

Target search page

You also need to add a src/search.md to display the results with the appropriate divs:

@def title = "Search ⋅ YourWebsite"

## Search

Number of results found: ~~~<span id="resultCount"></span>~~~

~~~
<div id="searchResults"></div>
~~~

Note that if you modify the id of these elements, you will need to adapt the lunrclient file(s) accordingly.

Building/updating the index

Franklin exports a lunr() function which

  • checks that you have the right files at the right place,

  • (re)builds the index, prepending a path to links if required.

If you are experimenting locally, just call lunr() then serve() and test that searching works as expected.

When you are ready to update your website you can either:

  1. (recommended) Call publish(final=lunr),

  2. Call lunr() or lunr(prepath) if there is a prepath and then publish your updates manually.

The publish(final=lunr) calls the lunr function as a last step prior to doing a git push. An advantage of using this is that Franklin will properly handle the prepath if there is one defined in your config.md.

⚠ Note
This final= keyword can be used with your own functions ()->nothing if you need to do some post-processing with the generated files before pushing.