What type of Jekyll plugin would a Flesch-Kincaid caclulator fall under?

Question

I'm wanting to write my first Jekyll plug-in. I've recently come across the flesch-kincaid algorithm for determining general reading level. What I'm thinking is to write something that adds a data attribute to each <p> tag or any element marked with [data-read-level].

Flesch Reading Ease Score = 206.835 − 1.015 × ( Total Words / Total Sentences ) − 84.6 × ( Total Syllables / Total Words )

What category does this fall under though? I'm thinking generator myself. Is there maybe some better way to show the results rather than an attribute?

I've written a somewhat working JS based version here, it needs work probably and only works with English right now.

JS Version:

// Flesch Reading Ease Score = 206.835 − 1.015 × ( Total Words / Total Sentences ) − 84.6 × ( Total Syllables / Total Words )

let fkExamine = function() {
    window.addEventListener('DOMContentLoaded', init);

    const fkConstA = 206.835;
    const fkConstB = 1.015;
    const fkConstC = 84.6;

    function init() {
      console.log('--      fkExamine.js initiated');
      let parseArray = [].slice.call(document.querySelectorAll('p, [data-read-level]'));
      parseArray.map(function(parseItem) {
        let txtContent = parseItem.textContent;
        let totalWords = getTotalWords(txtContent);
        let totalSentences = getTotalSentences(txtContent);
        let totalSyllables = getTotalSyllables(txtContent);

        let fkScore = fkConstA - fkConstB * (totalWords / totalSentences) - fkConstC * (totalSyllables / totalWords);
        parseItem.setAttribute('fk-score', fkScore);
      });
    }

    function getTotalWords(input) {
      const words = input.split(' ');
      return words.filter(word => word !== '').length;
    }

    function getTotalSentences(input) {
      return input.match(/[\w|\)][.?!](\s|$)/g).length;
    }

    function getTotalSyllables(input) {
      let syllables = 0;
      let words = input.split(' ');
      words = words.filter(word => word !== '');

      for(let i = 0; i < words.length; i++) {
        words[i].toLowerCase();
        words[i].replace(/(?:[^laeiouy]es|ed|[^laeiouy]e)$/, '');
        words[i].replace(/^y/, '');
        syllables += words[i].match(/[aeiouy]{1,2}/g).length;
      }
      return syllables;
    }
}();