fuzzyset_gramCounter.js

group = xs => xs.reduce((rv, x) => {
    (rv[x] = (rv[x] || [])).push(x);
    return rv;
  }, 
{});
objMap = (oldObj, func) => Object.keys(oldObj).reduce(function(newObj, current) {
    newObj[current] = func(oldObj[current])
    return newObj;
  }, 
{});

_gramCounter = function(value, gramSize = 2) {
  const normalized = `-${value}-` // use -dashes- to mark the beginning and end of words because these are more likely to be correct in misspellings
    .toLowerCase()                // converting to lowercase
    .replace(                    // removing non-alphanumeric characters
      /[^a-zA-Z0-9\u00C0-\u00FF, ]+/g,
      ''
    );
  const gramNum = normalized.length - gramSize + 1;
  const grams = [...Array(gramNum).keys()] // [0..gramNum]
      .map(i => normalized.slice(i, i + gramSize));
  // groups grams together  
  const groupedGrams = group(grams)
  // counts grams
  const countedGrams = objMap(groupedGrams, l => l.length)
  // return an object where key=gram, value=number of occurrences
  return countedGrams;
};