code: function withTrailingSlash (s) {
                      if(!IS_BROWSER && HAS_OS && require('os').platform === 'win32') return libs.string.withoutTrailingSlash(s) + '\\';
                      return libs.string.withoutTrailingSlash(s) + '/';
                  }
docs: Add a trailing slash to a string, if it doesn't already have one.
  If using Node.js, it will replace the trailing slash based on the value of os.platform
  (i.e. if windows, '\\' will be replaced, '/' otherwise).
  @param {String} s The string to operate on.
  @returns {String} The string without a trailing slash.
  @function