public/js/util/urlParameters.js

import _get from 'lodash/get';
import _set from 'lodash/set';

export function isValidValue(value) {
  if (value === undefined || value === '') {
    return false;
  }

  if (Array.isArray(value) && value.length === 0) {
    return false;
  }

  return true;
}

export function objectToParamString(obj, prefix) {
  return Object.keys(obj).reduce(function(soFar, key) {
    const value = obj[key];
    const encodedKey = encodeURIComponent(prefix ? `${prefix}.${key}`: key);
    if (!isValidValue(value)) {
      return soFar;
    }

    if (Array.isArray(value)) {
      return soFar.concat(value.map((subValue) => [encodedKey + '[]=' + encodeURIComponent(subValue)]));
    } else if (typeof value === 'object') {
      return soFar.concat([objectToParamString(value, key)]);
    } else {
      return soFar.concat([encodedKey + '=' + encodeURIComponent(value)]);
    }
  }, []).join('&');
}

export function paramStringToObject(string) {

  const stringNoQuestion = string[0] === "?" ? string.slice(1, string.length) : string;

  const params = stringNoQuestion.split("&");

  const paramsObject = params.reduce((paramsObject, param) => {
    const splitParam = param.split("=");

    if (splitParam.length !== 2) {
      return paramsObject; //Not key=value fail fast
    }

    const rawKey = decodeURIComponent(splitParam[0]);
    const rawValue = decodeURIComponent(splitParam[1]);

    const isArray = rawKey.indexOf('[]') !== -1;

    const key = isArray ? rawKey.replace("[]", '') : rawKey; // Strip off the [] if array
    const value = isArray ? _get(paramsObject, key, []).concat([rawValue]) : rawValue; // add to any existing values if array

    return Object.assign({}, _set(paramsObject, key, value));

  }, {});

  return paramsObject;
}