How to paginate Jekyll's data items using Liquid

Question

Hi I'm trying to access elements from the previous and next arrays. To be exact I want to access the previous and next url of pages. This is what I have done so far.Thanks!

{% assign page_venue = site.data.venues-array | where: "venueID",   page.venue | first %
//This outputs the current url
{{venue.url}}

This is part of the yml file:

venueID: Red-Radish
name: Red Radish
url: redradish
building: 65
neighborhood: University Union

venueID: Poly-Deli
name: Poly Deli
url: polydeli
building: 19
neighborhood: University Union

venueID: Myrons
name: Myron's
url: myrons
previous: MustangStation
building: 19
neighborhood: University Union

So let's say I'm the second venue (Poly-Deli), I would like to see this:
Current url: polydeli
Previous url: reddish
Next url: myrons
I tried using the following to output the previous and next urls but it dindn't work:

<p>{{page.next.url}}</p>
<p>{{venue.next.url}}</p>
<p>{{paginate.next.url}}</p>
<p>{{paginator.next_page}}</p>

Someone helped me, and it did work, but it outputs the whole list. I just want to output something like this because this because I have 30 arrays(30 different venues):
Current url: polydeli
Previous url: reddish
Next url: myrons

And this is the code that outputs the whole list:

{% for venue in site.data.venues-array %}

  {% assign next = forloop.index0 | plus: 1 %}
  {% assign previous = forloop.index0 | minus: 1 %}
    <div>Name: {{ venue.name }}</div>
    <div>Current URL: {{ venue.url }}</div>

    <div>Previous url:{{ site.data.venues-array[previous].url }}</div>
    <div>Next URL is:{{ site.data.venues-array[next].url }}</div>
    <hr>

{% endfor %} 

Answer 1

As I've mentioned in my previous comment, I was not able to find a suitable plugin to paginate a _data collection. There are a few available but all require a lot of hacking plus they are quite bloated for such a simple requirement.

You can add the following HTML and JS to the content part of your venues page. (I.e. underneath the front-matter).

HTML:

---
---
<div class="venue">

</div>

JavaScript:

<script type="text/javascript">

  /**
   * Setting for whether to keep looping or not.
   * If set to true, the first venue will show the URL of the last venue as
   * the previous venue, while the last venue will show the URL of the first
   * venue as the next one.
   *
   * If set to false, the first venue will not include a previous URL, while the last venue * * won't display the next URL.
   */
  var infinite = true

  // Gets all the venues adta and parses it as JSON.
  var venues = '{{ site.data.venues-array | jsonify }}'
  venues = JSON.parse(venues)


  // Inits the html content.
  var html = ''

  // The array index of the current venue.
  var currentVenueIndex = 0

  /**
   * Displays the current venue. Includes the previous and next links.
   *
   */
  var generateHtmlForCurrentVenue = function (venueName) {
    var venueContent = '<p>Current Venue Name: ' + venueName + '</p>' +

    getPreviousLink() + getNextLink()

    html = venueContent
  }

  /**
   * Gets the previous URL link unless we're not infinitely looping and the
   * current Venue is the first item in the array.
   */
  var getPreviousLink = function () {
    link = ''
    if (!infinite&& currentVenueIndex == 0) {
      return link
    }
    previousIndex = 0
    if (currentVenueIndex == 0) {
      previousIndex = (venues.length - 1)
    } else {
      previousIndex = (currentVenueIndex - 1)
    }

    return '<p>Previous: <a href="#" class="previous-venue">' +
      venues[previousIndex].url + '</a></p>'

  }

  /**
   * Gets the next URL link unless we're not infnitely looping and the
   * current Venue is the last item in the array.
   */
  var getNextLink = function () {
    link = ''
    if (!infinite&& currentVenueIndex >= (venues.length -1)) {
      return link
    }
    nextIndex = 0
    if (!(currentVenueIndex >= (venues.length - 1))) {
      nextIndex = (currentVenueIndex + 1)
    }
    return '<p>Next: <a href="#" class="next-venue">' +
      venues[nextIndex].url + '</a></p>'
  }


  /**
   * Shows the Previous Venue.
   */
  var showPreviousVenue = function () {
    if (currentVenueIndex == 0) {
      currentVenueIndex = (venues.length -1)
    } else {
      currentVenueIndex --
    }
    $('.venue').html('')
    generateHtmlForCurrentVenue(venues[currentVenueIndex].name)
    $('.venue').html(html)
  }

  /**
   * Shows the Next Venue.
   */
  var showNextVenue = function () {
    if (currentVenueIndex == (venues.length -1)) {
      currentVenueIndex = 0
    } else {
      currentVenueIndex ++
    }
    $('.venue').html('')
    generateHtmlForCurrentVenue(venues[currentVenueIndex].name)
    $('.venue').html(html)
  }

  /**
   * Previous venue link click event handler.
   */
  $(document.body).on('click', '.previous-venue', function (event) {
    event.preventDefault()
    showPreviousVenue()
  })


  /**
   * Next venue link click event handler.
   */
  $(document.body).on('click', '.next-venue', function (event){
    event.preventDefault()
    showNextVenue()
  })

  generateHtmlForCurrentVenue(venues[currentVenueIndex].name)

  $('.venue').html(html)

</script>

You can change whether to keep looping or not by toggling the infinite variable as explained in the code's comments.

Please note:

I have an older version of Jekyll on my system (v3.0.2) and thus the jsonify filter breaks when there are single quotes in the text values of the venues-array.yml. I.e. Myron's breaks and I could not escape it as shown below:

If you have the Jekyll >= 3.2 then I believe you will not have this issue as Jekyll will automatically use the UTF-8 encoding in advance of running the filter. I cannot upgrade my machine due to a client's site requiring this version and without a Docker container. If you do have this issue, try:

1) Enforce UTF-8 on your yml file. or 2) Clean up single quotes in advance of the filter or 3) Don't use single quotes :)

Escaping did not work for me.

Other than that, all works perfectly as shown below: