code: function ( urlToCheck ) {
    var DATA_URI_MATCHER = /^data:/gi, //regex to test for an url with a data uri
      PROTOCOL_MATCHER = /^http|^https:\/\//gi, //regex to test for an url with an absolute path
      RELATIVE_TO_HOST_MATCHER = /^\//g; //regex to test for an url relative to the host
  
    return urlToCheck.match( DATA_URI_MATCHER ) ? false : urlToCheck.match( RELATIVE_TO_HOST_MATCHER ) ? false : !urlToCheck.match( PROTOCOL_MATCHER );
  }
docs: check if this is a relative (to the document) url
  
  We need to rewrite if the url is relative. This function will return false if:
  - starts with "/", cause it means it is relative to the main domain
  - starts with "data:", cause it means is a data uri
  - starts with a protocol
  
  in all other cases it will return true
  
  @param urlToCheck the url to test
  @returns {boolean}