submit-social-housing-lettings-and-sales-data/app/frontend/modules/search.js

const addWeightWithBoost = (option, query) => {
  option.weight = calculateWeight(option.clean, query) * option.clean.boost;

  return option;
};

const clean = (text) =>
  text
    .trim()
    .replace(/['’]/g, "")
    .replace(/[.,"/#!$%^&*;:{}=\-_`~()]/g, " ")
    .toLowerCase();

const cleanseOption = (option) => {
  option.clean = {
    name: clean(option.name),
    nameWithoutStopWords: removeStopWords(option.name),
    boost: option.boost || 1,
  };

  return option;
};

const hasWeight = (option) => option.weight > 0;

const byWeightThenAlphabetically = (a, b) => {
  if (a.weight > b.weight) return -1;
  if (a.weight < b.weight) return 1;
  if (a.name < b.name) return -1;
  if (a.name > b.name) return 1;

  return 0;
};

const optionName = (option) => option.name;
const exactMatch = (word, query) => word === query;

const startsWithRegExp = (query) => new RegExp("\\b" + query, "i");
const startsWith = (word, query) => word.search(startsWithRegExp(query)) === 0;

const wordsStartsWithQuery = (word, regExps) =>
  regExps.every((regExp) => word.search(regExp) >= 0);

const calculateWeight = ({ name, nameWithoutStopWords }, query) => {
  const queryWithoutStopWords = removeStopWords(query);

  if (exactMatch(name, query)) return 100;
  if (exactMatch(nameWithoutStopWords, queryWithoutStopWords)) return 95;

  if (startsWith(name, query)) return 60;
  if (startsWith(nameWithoutStopWords, queryWithoutStopWords)) return 55;
  const startsWithRegExps = queryWithoutStopWords
    .split(/\s+/)
    .map(startsWithRegExp);

  if (wordsStartsWithQuery(nameWithoutStopWords, startsWithRegExps)) return 25;

  return 0;
};

const stopWords = ["the", "of", "in", "and", "at", "&"];

const removeStopWords = (text) => {
  const isAllStopWords = text
    .trim()
    .split(" ")
    .every((word) => stopWords.includes(word));

  if (isAllStopWords) {
    return text;
  }

  const regex = new RegExp(
    stopWords.map((word) => `(\\s+)?${word}(\\s+)?`).join("|"),
    "gi"
  );
  return text.replace(regex, " ").trim();
};

export const sort = (query, options) => {
  const cleanQuery = clean(query);

  return options
    .map(cleanseOption)
    .map((option) => addWeightWithBoost(option, cleanQuery))
    .filter(hasWeight)
    .sort(byWeightThenAlphabetically)
    .map(optionName);
};

export const suggestion = (value, options) => {
  const option = options.find((o) => o.name === value);
  if (option) {
    const html = `<span>${value}</span>`;
    return html;
  } else {
    return `<span>No results found</span>`;
  }
};

export const enhanceOption = (option) => {
  return {
    name: option.label,
    boost: parseFloat(option.getAttribute("data-boost")) || 1,
  };
};