index.js

const twoStrings = (sa1, sa2) => {
  // Compare two strings to see how similar they are.
  // Answer is returned as a value from 0 - 1
  // 1 indicates a perfect similarity (100%) while 0 indicates no similarity (0%)
  // The algorithm is an n-gram comparison of bigrams of characters in a string

  // Comparison should not check case or whitespace
  let s1 = sa1.replace(/\s/g, "").toLowerCase();
  let s2 = sa2.replace(/\s/g, "").toLowerCase();
  if(s1.length === 1 || s2.length === 1) return Number(s1 === s2)
  const similarity_num = 2 * intersect(pairs(s1), pairs(s2)).length;
  const similarity_den = pairs(s1).length + pairs(s2).length;
  return similarity_num / similarity_den;
};

// private functions ---------------------------
const intersect = (arr1, arr2) => {
  let r = [],
    o = {},
    l = arr2.length,
    i,
    v;
  for (i = 0; i < l; i++) {
    o[arr2[i]] = true;
  }
  l = arr1.length;
  for (i = 0; i < l; i++) {
    v = arr1[i];
    if (v in o) {
      r.push(v);
    }
  }
  return r;
};

// private functions ---------------------------
const pairs = (s) => {
  // Get an array of all pairs of adjacent letters in a string
  let pairs = [];
  for (let i = 0; i < s.length - 1; i++) {
    pairs[i] = s.slice(i, i + 2);
  }
  return pairs;
};

// Sort array with dice Comparator
const simSort = (s1, arr1) => {
  // Comparison should not check case or whitespace
  return arr1.sort(function (a, b) {
    let v1 = twoStrings(s1, a);
    let v2 = twoStrings(s1, b);
    return v2 - v1;
  });
};

exports.twoStrings = twoStrings;
exports.simSort = simSort;