code: function checkUrl(url, resourceName, hrefKey) {
      if (url == undefined || !url) {
          throw new Error("The provided resource name '" + resourceName + "' has no valid URL in the '" +
          hrefKey + "' property.");
      }
      return url
  }
docs: Checks the given URL if it is valid and throws a parameterized exception containing the resource name and the
  URL property name.
  
  @param {string} url the URL to check
  @param {string} resourceName the name of the resource
  @param {string} hrefKey the URL property key
  @returns {string} the URL if it is valid
  @throws Error if the URL is not valid