Add query string to a URL

Question

I have written this code which adds a querystring to a URL:

exports.addQueryString = function(url, queryString) {
  var isQuestionMarkPresent = url && url.indexOf('?') !== -1,
    separator = '';

  if (queryString) {
    separator = isQuestionMarkPresent ? '&' : '?';
    url += separator + queryString;
  }

  return url;
};

Is there any way I can write this better?

Usage:

addQueryString('http://example.com', 'q=1&val=3&user=me');

Answer 1

I think that is ok, only that i see not necesary make url.indexOf('?') if queryString is empty, because you are not going to use it.

exports.addQueryString = function(url, queryString) {   
  if (queryString) {
    var isQuestionMarkPresent = url && url.indexOf('?') !== -1,
      separator = isQuestionMarkPresent ? '&' : '?';
    url += separator + queryString;
  }

  return url;
};

Answer 2

What happens when you just want to add a single queryString to and already long queryString? You would need to know the entire queryString to do that, just to add a single new value.

What your function should do is take a single queryString value and if it already exists it should update it and if it doesn't exist it should append it.