Parse query string. use Underscore.js.

getQueryParams.js

/**
 * Parse query string.
 * ?a=b&c=d to {a: b, c: d}
 * @param {String} (option) queryString
 * @return {Object} query params
 */
getQueryParams: function(queryString) {
  var query = (queryString || window.location.search).substring(1); // delete ?
  if (!query) {
    return false;
  }
  return _
  .chain(query.split('&'))
  .map(function(params) {
    var p = params.split('=');
    return [p[0], decodeURIComponent(p[1])];
  })
  .object()
  .value();
}

// --- Jasmine test

describe('_.getQueryParams', function() {
  it('?a=1', function() {
    var result = _.getQueryParams('?a=1');
    expect(result).toEqual({a: '1'});
  });
  it('?a=1&b=2', function() {
    var result = _.getQueryParams('?a=1&b=2');
    expect(result).toEqual({a: '1', b: '2'});
  });
  it('?a=1&jp=ほげ&en=Hoge', function() {
    var result = _.getQueryParams('?a=1&jp=%E3%81%BB%E3%81%92&en=Hoge');
    expect(result).toEqual({a: '1', jp: 'ほげ', en: 'Hoge'});
  });
  it('?a=1&jp=%E3%81%BB%E3%81%92&en=Hoge', function() {
    var result = _.getQueryParams('?a=1&jp=ほげ&en=Hoge');
    expect(result).toEqual({a: '1', jp: 'ほげ', en: 'Hoge'});
  });
  it('?a&b=2', function() {
    var result = _.getQueryParams('?a&b=2');
    expect(result).toEqual({a: 'undefined', b: '2'});
  });
  it('', function() {
    var result = _.getQueryParams('');
    expect(result).toEqual(false);
  });
});