QueryParams - super-simple query string parser with comma-delimited arrays

QueryParams.js

const QueryParams = {};

QueryParams.options = {
  usePlusSigns: false, // per RFC 1866 application/x-www-form-urlencoded; otherwise use "%20" for space
  keyMustReturnArray: key => key.endsWith('_arr') // for URI-decoded keys that return `true` for this function, coerce the value to an array even if it contains no commas
};

const decode = str => {
  if (QueryParams.options.usePlusSigns) {
    str = str.replace(/\+/g, '%20');
  }
  return decodeURIComponent(str);
};

const encode = str => {
  str = encodeURIComponent(str);

  if (QueryParams.options.usePlusSigns) {
    str = str.replace(/%20/g, '+');
  }

  return str;
};

QueryParams.parse = queryString => {
  const obj = {};

  const m = queryString.match(/\?(.+)/);

  if (!m) return obj;

  const data = m[1];

  data.split('&')
    .forEach(kv => {
    const [_key, val] = kv.split('=');

    const key = decode(_key);

    if (typeof val === 'undefined') {
      obj[key] = null;
    } else if (QueryParams.options.keyMustReturnArray(key) || val.includes(',')) {
      const arr = val ? val.split(',') : [];
      obj[key] = arr.map(el => decode(el));
    } else {
      obj[key] = decode(val);
    }

  });

  return obj;
};

QueryParams.serialize = obj => {
  let queryString = '?';

  Object.keys(obj).forEach((key, idx) => {
    const val = obj[key];

    if (typeof val === 'undefined') return;

    if (idx !== 0) queryString += '&';
    queryString += encode(key);

    if (val === null) return;

    queryString += '=';

    if (val instanceof Array) {
      queryString += val.map(el => encode(el)).join(',');
    } else {
      queryString += encode(val);
    }
  });

  return queryString === '?' ? '' : queryString;
};

QueryParams.get = () => QueryParams.parse(window.location.search);

QueryParams.set = (obj, usePushState=true) => {
  const f = usePushState ? 'pushState' : 'replaceState';
  window.history[f](
    {},
    '',
    [
      window.location.origin,
      window.location.pathname,
      QueryParams.serialize(obj),
      window.location.hash
    ].join('')
  );
};

QueryParams.update = (obj, usePushState=true) => {
  const updates = QueryParams.get();

  Object.keys(obj).forEach(key => {
    updates[key] = obj[key];
  });

  QueryParams.set(updates, usePushState);
};

QueryParams.clear = (usePushState=true) => {
  QueryParams.set({}, usePushState);
}

export default QueryParams;